I have the 4.24:1 like I said earlyer.
I love them most of the time, but at times I wish they were steeper. Mabe 6:1?
My forth gear is like driving 1st gear 4wd to give you a comparison.
You really have to deside what tire your running and where you want to go.
I can put it into 1st and full lock and can easally motor through rocks and logs without burning up my clutch.
I run sand all the time but I do that in 2wd! It's a lot more fun that way. There's only one hill I can't make up that way. So I get to the bottom, put it in low - 4th gear, then run it up to 6k. Make it to the top almost every time!

(Though I will admit that the stock low gearing was the best for sand.)
As for mud it gives me plenty of low end torque to keep the tires moving fast enough to clean them out. The only time I get stuck in mud is when I bottom out, not lack of wheel speed.
I don't know what 3.5:1 would be like, but I don't have any trouble keeping up with anyone on the trail. If I need more speed I usually need 2wd and a lot higher speeds.
Lastly it could make a big difference if you have a auto or stick. An auto might be able to make up the difference in the converter were a stick you will need more clutch.