Both seem largely /shrug. 9-piece is pretty much a non-starter just due to how much time it would take to get 9 semi-decent items. Supersonic seems especially useless. Merciless 3-piece seems okay, though going with 3 pieces means you're breaking some other bonus in the process.

Both should be strong, personally I favor Merciless over Supersonic.  Either way it's likely gonna take a bit to get a really good set.

They're gonna be quite strong, Lyryal. For me at least, they are strong enough it's worth focusing whatever percentage of my playing time is required to maximize obtaining as much of it as I can. 

And sure, their full effects are just crazy, but since they are never "broken" sets, they can do some serious heavy lifting in piecemeal builds.