I like option 1 better. There is a ton to do in UT. I went with my daughter when she was 11 for the first time. She is 19 and I have been back to Utah 6 or 7 times in that span. My point is this--slow down and do each location right and don't just fly through them. My very favorite thing I have done in UT was www.deserthighlights.com. very safe and your son would love it. We also really like www.soaringcolorado.com in Durango. This is very expensive but also includes the train and lunch. Most of the places you mention deserve 2 days. Even Mesa Verde deserves 2 days, IMOP. You can do the GC in a day, unless you plan on hiking a lot there.
One other thing. Goblin Valley State Park is an excellent place in UT. Little Wildhorse Canyon is 10 minutes from there. You really need a half to full day along HWY 12 too. Plenty to see and to in that section.

Check rates flying into Durango, Grand Junction, and Moab. Even tiny Cortez, CO. rates might be as low as CO Springs.

You might want to consider roughing it and go tent camping. Weather would most likely cooperate for that month and not be that hot or that rainy(of course, one never truly knows). It would save you a ton of money.

The North Rim of the Grand Canyon would be far closer to the other areas you mention. However, most consider a first time visit to the GC to be a must on the south side. There is far less people on the north and more trees-less deserty looking

I like trip 1.

Get as early a flight into Colorado Springs as you can and head towards Mesa Verde that day to get a few hours off what will be about a 7 hour trip that first day, so you probably won't be able to go all the way after the flight.

Get a National Park Pass at the first park. It is $80 and good for all parks for a year.

If you can, get lodging in the parks or in a nearby motel with a pool. Mesa Verde and Grand Canyon are far enough from lodging that if you can get in park lodging it will maximize your time in the parks.

We enjoyed a half day smooth water raft trip on the Colorado River from Page - Glen Canyon Dam - to Lees Ferry.

Really there's not much difference in the two itineraries, just swapping out Mesa Verde for Sedona. Page is doable with both trips.

You will want to check the drop-off fee for the car rental, it may be much cheaper to just make a round trip from Las Vegas for either trip.

Our family who live in Colorado Springs fly in and out of Denver... not sure why you list CSprings as the arrival city since it is just a quick to drive as it is to change flights for the short hop unless you have connections with the airforce.

And definitely check the car rental drop off fees as WhereareWe says. They may double. It is possible that between Phoenix and LV there are enough takers that you wouldn't have the issue between those two cities.

Otherwise either itinerary looks fun with lots of options for a great trip and lots of memories. I wouldn't put one over the other. You will find there is too much to chose from for a 6 day trip. The important thing is not to try to do it all. Just enjoy what you do.

You could easily find enough to do in just Utah or just Colorado. Rocky Mountains would be nice this time of year too. Elk Rut and Fall Foliage.