Hello SR, I have been to Kavieng but not Uepi.
First thing I would check is whether Uepi was affected by the earthquake last year. I'm pretty sure it wasn't as it's pretty far from Gizo, but you should ask somebody who has been there recently. I was told by an Indonesian friend that it can take many years for a reef to recover from a tsunami, he would know as he dives all over his country and has seen the before/after in many places.
Otherwise, I'd bet Uepi has very good diving, but probably not quite as much macro diversity as Kavieng. I was amazed at all the little stuff I saw in Kavieng-saw my first inimicus there-not to mention all the big stuff-sharks, pelagics-and great viz. Also saw some monster turtles, several huge schools of mobula rays, and some WW2 wrecks, including a Japanese midget sub. But aside from the macro, it seems like a close call. Are there any wrecks near Uepi? But, there are probably more dives that involve heavy current in Kavieng than Uepi, if you're current averse.
If you do wind up in Kavieng, make sure the operator you choose has a
boat capable of making it to New Hanover and back in reasonable time, which is where the midget sub and some other very good dives are... -Andy