[popcornmix]

Should we be leaving both players (omxplayer & the other one; forgetting what it's called right now) enabled in Settings?

That's what official stable/Helix builds do.
These test builds disable omxplayer by default as that's the future plan.

Basically omxplayer has better performance, but misses some features (e.g. ALSA audio, DVD menus).
Some thing just work a bit differently.

On Pi1 using omxplayer was essential for Bu-Ray quality video.
On Pi2 you can play Blu-Ray video without omxplayer (dvdplayer with MMAL codec acceleration).

However there's a couple of use cases where even on Pi2 performance is better with omxplayer (mostly live TV with deinterlace enabled).
I think these issues are solvable, but for now omxplayer has some advantages.

I normally run with omxplayer disabled. That would be my recommendation if it works well for you.
If you have any performance issues (especially with live TV and interlaced content) then try enabling omxplayer.

For most users they both work fine, and it's hard to tell which one you're using without checking.