Any of you use either of those while running? I'm considering getting a pair so I won't have to wear a base layer for my half next month. I'm assuming the race will start off with cooler temps but as I'm moving along I know I'll warm up but I don't want to be freezing the first few miles if I don't have to. I'd hate to have on clothing I couldn't take off right away and wearing something around my waist isn't an option. I am, however not opposed to just getting a throw away top, but that just seems wasteful. I typically run in sleeveless tops and tri shorts but the temps here in the South warrant it almost year round, and even in the "winter" I'm still in some sort of short sleeve top and shorts, unless it's unusually cold then I'll wear a long sleeve top and shorts.

Pros? Cons? Favorites?