I went with 4.10. I maintain a pretty lightweight Jeep and my adventures are solo. I run 33s, and if I do go to a "35" it won't be a true 35 but instead one that measures in the 33"-34" range. I bought a set of gears from Nitro, including a master install set, and a new carrier for my front differential as the new gears needed it. The labor ran $1000 even, and the gears and carrier ran $800. I have heard excellent things about Yukon's gears, but they don't make 4.10s.What size did you go with? I so badly want to replace my 3.21s. They do fine with my on the highway and pulling the Supra Sunsport, but when I go up to 35s, I'm sure they will be just aweful. What was your total cost on the upgrade?
Assuming you're running a JK, here are a couple of charts that may help you. The tire sizes listed here are the measured size, not the advertised size. These charts are also just guidelines. If you're hauling a heavy load, like the trailer, you might want to err on the side of performance. I hope this helps!