None! The thinking is the thicker the lug, obviously the stiffer it is! But I can’t see getting thicker than .250”....even for the ultra magnums. And parallel or straight is a difference for easier fitment/bedding issues. The reason you see see so many flavors is because of the buyers market! If someone says they “need” it, a manufacture will make it!

I would stick with .250” thick, and go with whichever shape is most appealing to your eye. Won’t make a bill a beans difference performance wise.