Quality / Money / Features , Zoom has been performing great ever since the first release of their Zoom H4. I've owned Zoom H4,H2,H1,R16,Q2HD,Q3HD and would grab any new Zoom toys but I had to outgrow and move on to higher end audio interface when the opportunity came knockin. I still own the Zoom H1 though. love it!
the difference between the H5 and H6 mainly it's $200+/- difference and you're paying $100 per simultaneous track support. so one records 4 tracks simultaneously, the other goes up to 6 tracks for more flexibility/upgradability.
if you want to get a great multi drumtrack from a light weight setup I could imagine,
Zoom H6 (on a mic stand as overheads #1,2) , #3-snare,#4-kick,#5-tom,#6-tom. got lots of toms? #5,6 = submixer (pan it well!) to more toms. but I'd just sandwich the #5tom mic in between the left/right tom.
want a easy demo recording? #1,2 = drumoverheads , #3-put a mic on a cloth on the kickdrum facing the drummer's crotch. yes it's the crotch-mic technique. #4-guitar,#5-bass,#6-vocals (or if you have another guitarist. make it so. then vocals layer it when at home using the zoom's onboard stereo mic)
but if you want bigger than this, then i recommend getting a 2nd hand zoom r16 (i bought mine for $500 in 2009, sold last year for $280) or zoom r24
so big question is, what do you intend to record/do/accomplish with it?