What engines are you looking at getting in it? Are those 4 and 6 speeds manuals or autos? What do you plan on towing?
My powerstroke has 3.55 gears and a 5 speed manual. I was told the 6 speed manual would only give me a lower 1st gear. They are great when not towing or not towing a heavy load but when I get towing heavy loads it really has to big of a gap between the gears and I wish I had 4.10's or a spliter on it. Still I hate to give up the 19mpg I get with the 3.55 gears when not towing. I think 3.73 would be a good compromise.