There seems to be little middle ground on the M5--most people either hate it or love it. If you haven't used one of the other Leica M cameras, it may suit you okay. If you have used other M bodies, the M5 seems foreign. It's bigger with the levers and other controls being in different places. It wasn't very "Leica-like" to camera buyers when it was released so it didn't do well in the marketplace.
I like the M6 "classic" (non-TTL). I don't use flash so the TTL option doesn't appeal to me and the shutter speed dial on the TTL models operate in the opposite direction than other Leicas. Some like the TTL dials because they turn in the direction of the lighted arrows of the exposure meter.
'Course all this just comes down to personal preference, like just about everything else in the world.