I think either option will accomplish the same thing: reduced sun exposure. For me, it's sort of a mental thing. I have a mental block when it comes to wearing a long sleeve jersey in summer, despite the fact that I've done it while sailing and it's really not any hotter than short sleeves. I prefer the arm coolers because I know that I can peel them off if they do get too hot and it's easier (IMO) to re-apply sunscreen under them if necessary.

I do like the looks of that Ground Effect jersey though... Hmmmm....