Durability-wise, Subaru headers seem worse than most. If you're set on them, stick to top-quality. Fed up, I finally went back to manifolds (PnP, with with x-pipe and uppipe).
But that wasn't the question you asked...
Between EL and UEL, EL is theoretically superior- though there's scarce empirical data to support the notion, and there's plenty of high powered cars running UEL. I made more power after ditching my EL for my PnP setup. Not that my stage 2 setup relates to your build, but is an interesting data point that suggests that notions aren't always validated on the dyno.
IMHO, the primary decision point is the sound- header type changes it a lot. Obviously, that is a personal preference which only you can answer. Lots of sound clips on YouTube to compare...