The knives I carry most often are Spyderco/Byrd knives, with thumb holes, so I guess that's what I prefer because I use it more often. i can get by just fine with a flipper, however...thumb stud, also acceptable as long as it doesn't bite into the thumb and take skin off. It's not that I really prefer the Spydie hole...it's just that of all the knives I own I prefer my Spydies, so they get the most pocket time. If I run into a design that I just love, and it doesn't have a thumb hole, that;s not a deal breaker, and I will adjust to it just fine.
I generally don't use my knives when I have gloves on. Being a student in suburbia, I don't find myself outside needing to cut things very often, and if I do, it's not for an extended period of time, so I usually just take my gloves off (especially because if I do have to cut something in a public place, outdoors, I'm more prone to reach for either a slipjoint or small MT I have in my pocket).