I don't think I'd be keen on paying the difference for WT+/E+ for either BA or UA.
BA asks about US$400 more (return) for WT+, give or take. It seems that many don't think WT+ is really worth that price, but instead, it's a stepping stone to a J upgrade, either due to overbooking or for miles.
On the other hand, with *A status, I've been upgraded to E+ on UA without lining any pockets or wondering if that $400 investment will pay off.
--Grog--