Let me tell you a few things;

First, I'll comment about Snorkeling. Walk-in snorkeling anywhere on Nevis is almost non-existent. You'll see a few small fish but no coral around the man-made breakwaters in front of the Four Seasons' beach and there's a very small natural reef (you can see everything there is to see in under 10 minutes) 150 feet or so off of Herbert's Beach on the northern side of the island. The best snorkeling (any it is only mediocre) in the area is off of Shitten Bay on St. Kitts - it's accessible only by boat (you can do a 1/2 day sail tour right from the Four Seasons' dock) - that's about it. To put it blunt NO ONE goes to Nevis for the snorkeling. I don't recall there being any walk-in snorkeling at Carlisle Bay but there are a few spots on other beaches around the island where you can walk-in snorkel. The better snorkeling areas around Antigua are accessible only by boat but they pale in comparison to what you'll find in places like the USVI's, the BVI's and Bonaire. Bottom line neither Nevis or Antigua are noted for great snorkeling.

Second, both resorts offer small sailboats like Hobie Cats and/or Sunfish and windsurfing equipment. I don't recall seeing anybody on paddle boards. I'm pretty sure at Carlisle Bay the boats, etc. are complimentary. You'll pay an hourly rate to use them at the Four Seasons.

Third, you'll find more hiking opportunities on Nevis than you will on Antigua but I'm not sure that will make much difference for the "average vacationer" as how many hikes can you go on in a typical week long trip.

Fourth, You are correct, in May, I doubt you'll children at either resort will be an issue.

Fifth, while neither islands is considered a "shopping mecca" you'll find more shops on Antigua than you will on Nevis.

Sixth, calmness of waters at either resort is going to be dependent on Mother Nature but more than likely it will be calmer at Carlisle Bay. Also, the near shore waters on Nevis will not be as shallow as the waters off of Antigua's beaches.

Seventh, you can go horseback ridding on both islands but you'll have to go "off-resort to do it on both islands.

Eighth, There's good a good variety of "off-resort" dining on both islands but I'd give Nevis slightly higher marks especially if you are looking for upscale dining.

Ninth, According to my spouse Four Seasons has one of the best spas in the Caribbean. My spouse was also happy with the Spa at Carlisle Bay. I don't like spa treatments one bit so I won't comment any further.

Thanks so much for your advice. The last question I have is how the resorts compare in terms of atmosphere or "feel".

I know the FS is about twice the size, but does it feel twice the size? Does the FS have a specifically Nevisian vibe? Or does it have an impersonal, this-could-be-a-Four-Seasons-anywhere vibe?

Does the Carlisle feel more exclusive/upscale?

How do they compare in terms of remote-ness? Is there non-resort traffic (vendors on the beach, watercraft, etc.)?

Although the Four Seasons is quite extensive in terms of land area the resort itself doesn't feel "twice as large" mainly because the golf course and the private villas are spread out around the property. The main resort buildings, while clustered near the beach, are positioned in such a way as to be somewhat hidden from each other by gardens and landscaping. Besides, you are going in May, the resort will in no way be crowded.

There are no vendors on either beach and both resorts are pretty well self-contained so you won't see any outsiders unless you venture off resort. The only water traffic you'll see nearby are boats belong to the resorts and, at the Four Seasons, perhaps one or two mega-yatchs anchored 1/4 mile or so off-shore while their owners spend a few nights at the resort.

Both resorts have "Caribbean vibes" and personalized service. FYI - Four Seasons' staff is trained to quickly learn your names and will always greet you with a "Hello, Mr. & Mrs, LAST NAME". I don't think one has a more "upscale feel" than the other - pretty much a tie in that area.

We have not stayed at Carlisle Bay BUT have stayed aty FS Nevis...it was fantastic! We really loved it!

Great, thanks. When I was referring to size, I should have been more specific: I believe the FS has more than twice as many rooms as CB. On our trip to Turks and Caicos, we liked the relatively intimate feel of Parrot Cay in comparison to the bigger resort-y Grace Bay Club. I was thinking there might be a similar dynamic at play with these two resorts.

However, your answer makes it sound like the FS is designed in such a way as it doesn't have a resort "sprawl" effect, i.e. where you look out across multiple pools, bars, and restaurants and potentially dozens of other guests.

Thanks again. Your advice is very helpful.

You won't see bars or restaurants from any of the rooms at the Four Seasons. Depending on your room location Views will either be: 1) spectacular ones across the golf course towards Nevis Peak, 2) wonderfully landscaped gardens or 3) through groves of palm trees and/ or gardens toward the Caribbean Sea. Although there are three pools on the property they are very well screened and difficult to see from the rooms. Likewise, the tennis courts, parking lots and service buildings are all screened from general viewing.

Again, in May you won't encounter a lot of other tourists either on or off resort. Even in "High Season" the resort never feels crowded.

Haven't been to Carlisle in Antigua, but do know both islands reasonably well. Think Nevis sounds like it will meet your criteria better. Excellent hiking and biking on Nevis, much easier to get around if you hire a car for a day or two. FS on a fab beach - walk along beach to Sunshine's for a relaxed drink. Horseback riding on the beach. Nevis will probably be quieter, kids will still be in school in May on both islands. Could easily do a day trip to St Kitts by ferry or air shuttle.

"Sunshine's" Brings back great memories...yum!

Have not been to Carlisle but stayed at FS Nevis (Nov 2012) for the 4-0 bday and can not say enough great things about the resort. The service was outstanding especially at the beach and pool. We left kids at home so it was so relaxing. The minute we stepped on the FS boat from St Kitts it was paradise. The FS staff was the friendliest bunch of any of the islands we have been to. There is nothing they can't do. One morning we did the horseback ride. It was a combination of beach, trails, and going through some villages- Loved it!! Spa was top notch- just sitting in the relax area looking at Mt Nevis was amazing. We took the FS sail / snorkel trip over to St Kitts. The area is not known for snorkeling compared to other places we have been but it was still worth the trip and we did see some cool sea life
( lobster, big sea turtle, etc). We did not play golf but really enjoyed walking/running the trails they have around the course. Really fun to see the villas, monkeys, spectacular sea views and St Kitts in distance.
My only regret is only staying five nights. I wish we had done some hiking and an island tour but ran out of time.
Great food too on resort and island. Don't miss Montpelier sugar mill.

Good luck deciding!

We have just returned from the Four Seasons Nevis (last week) and the one thing I will add to the above is that we booked a mountain view room and loved it. I think it was the least expensive room category but really I found the view of the mountain mesmerizing and watching the clouds change color right before sunset was extraordinary. I also liked the location of these rooms.

When we booked the room we were not eligible for both the 4th night free promotion at FS and the AMEX benefits so you might want to double check if you were counting on that. Perhaps the Four Seasons is offering both now for a May booking.

It was our first time to Nevis and we absolutely loved it. I would say you won't find shopping there but you will find great food, hiking, bicycling and gracious people.