I've used a version of the Oval Concept.

Plusses in my mind include:
- Oval makes nice stems to begin with in many lengths/angles/weights
- Versatility, Oval allows you to setup in whatever way you want, above, below, pads above, extensions below, s-bends, straight extensions, etc...
Minuses:
- setup is a little finnicky, it's not something I would want to take off/put on regularly
- You need to use a fairly horizontal stem because your stem angle governs your aerobar angle
- Costly, I had an old set of extensions and pads but damn it seems like a lot to me

Profile, I haven't used but here are some thoughts from seeing it in the store -
The Profile looks easier to put on/take off
The Profile stems are more limited and not as nice IMO
It's even costlier from what I can tell
Not as adjustable/customizable
Looks nice though