hey all, had to add my input here. I've been going through the media player hell also, finally am trying mort for the first time.
I'm experienced with meridian (great features, don't love the UI but it's ok, plenty of codec support + video playback, very professional, seems, but I could be simply getting a placebo effect here, that it's a little higher on the resource use than some other players).
stock player: ewe, blech. major resource hog on my 2.2 phone (froyd 1.5).
mixzing: not sure about this one yet, seems relatively light on resource use (nice), plenty of amazing features, but free version is missing stuff I want. of course, tha'ts how they sell the full version right? Just not sure yet about it, I think it's pretty good, and has built in defeatable EQ, a very nice thing to see finally on android. UI is vaguely similar to meridian, good enough, not super original, but very usable (mimicking my thoughts of meridian).
btunes: nice UI, I'm not an itunes lover (actually dislike some of it's UI, sorry apple, love you guys!). seems nice and relatively low resource use, but I find the playlist concept confusing. maybe that's why I don't like itunes all that much also?

so could just be my preference, but I found it confusing.
mortplayer: wow, i like the UI better imho, I like the relatively light weight resource use (so far, will know mroe after further testing), I'm old school, I like it to play my folder structure, not my playlists (which is how I always setup my ipods too fwiw). Just not a playlist guy I guess. it's like, why create a playlist? the album's already in a folder organized by artist/album. Lots of extra work for only one specific feature that I can imagine is worth using a playlist for - making a mix playback (one song from this album, one from that album, and so on). Otherwise, playlists = I just don't get it.
There are others I've dabbled in too - lithium, cool look on player screen, nice animated spinning thing, but seriously, what's so good about this player? I didn't spend much time wtih it though, so limited in features from what I got out of it. Maybe I just don't get it, but too light weight in UI/features for me. 3Cubed... erm... let's play where did the widget disappear to and how do you place the invisible widget? ooooooooook. cool cube thing, totally not taking advantage of how it could utilize that UI however, and the player itself is pretty basic from what I recall, cover art worked sometimes, not others, and I kept losing the player controls in the widget. Maybe just me... but doesn't seem even ready for beta yet imho.
So there you go. My current choice is mortplayer.
like it. widget actually has useful controls on it as well fwiw. swiping works great, no stupid files being picked up that I don't want to play, this is jsut a better way of finding your music. At least for me
Sound quality I'm not sure about yet - haven't done serious comparisons yet, but I get the feeling that mort has better sound quality than some others. Could very well be in my head though, I have done ZERO true comparisons and ZERO blind abx comparisons. Nor any tests with equipment.
If I get serious about this then I'll actually take it into my recording studio and do some real analysis to see how things turn out, but I'm so short on time these days I wouldn't expect that to actually happen, sorry.
Other thing is battery life - but I think my hero sucks with all of them. If one stands out as better I'll let you know. I know cpu is different between different players, but hard to measure so far for me. just how my phone works while playing music is my own subjective test at the moment... how well applications menu scrolls in launcher pro while playign music, etc etc