I will throw in my .02, but it is from one trip to cozumel. I dove Blue XT Sea primarily and Dressel on an afternoon.
Blue XT has nice boats with some shade for getting out of the sun. The DM's are knowledgable and handle your gear from start to finish. You are pampered and taken care of from the time you get in the boat until you leave it...your gear is rinsed and hung back at their shop to dry....waiting for you on the tank the next morning when they pick you up. Surface Intervals are on the beach at a local resort, restrooms etc are there if you need them. If the wind is blowing just wrong, they SI at what I took to be an abandoned pier, but it's a nice beach and comfortable place to siesta. They provide bottled water, juice, fruit and muffins on your surface interval along with dry towels and jackets for those who want them. You dive your computer, no time limits. We started our ascent at 700 psi regardless of depth but we are novices and I think Blanca was keeping us safe, which I thank her for. Entry is a back roll over the side, which I enjoy.
With Dressel you are on a clock. 1 hour in the mornings, 45 minutes in the afternoons. When the DM's clock says it is time, you are going up. As a novice that only cut me out of about 10 minutes worth of diving on the two afternoon dives I went with them...for an expert you might end up in the boat with a tank you could dive again.
Entry is giant stride off the back.
I would dive with Blue XT Sea again without question. Dressel...only if the Op I booked the rest of the week with wasn't doing afternoons, and then only if I was really wanting to keep going. Their DM's were friendly, the boat was crowded but not enough to bother me, the schedule where you can pick which dives you want is pretty cool. Nitrox is free, which is very cool. But I find that I don't like being on a timer. If that means I won't get afternoon dives in the future...well so be it I guess (though I would rather have my cake and eat it too).
Spend some time in the coz section here and read a lot. Have contingency plans for if the weather doesn't allow diving, or if it's only suitable to dive the east side, or cenotes. I went through the same decision process you are going through a month or so ago. I decided on Blue XT Sea and don't regret that decision.
We went down with the plan of diving 6 days, 1 day to tour the island..come home. 3 days of weather came in and we had no idea what to do with ourselves after the first one. Next trip, I will know better. There are zip lines on the island which would pass half a day in a fun way. I thought the ruins were unimpressive, but others like them. The ruins on the mainland are better if you have the entire day off. Aldora dives the east side if it's a Norte holding you up (others may as well). We toured some hotels etc on the last weather day, which has helped us plan our next trip. You can swim with the dolphins if that sounds fun. I'm sure there is a lot to do on the island when diving isn't possible, but I had not even considered the possibility when we went, which was my mistake. Make a list, print websites etc and take it with you...just in case.