I like the Jackson 5 singles from '69-'72.
I like the jacksons singles from '76-'79.
I like the catchy 'bubble-gum-soul' of the Jackson 5:heart:, but it's very much before my time in terms of lyrics, recording techniques, etc. not a fan of loud drums either..
with the jacksons, I prefer this phase of Michael's voice. the music sounds more polished and varied. what really edges it out is the performance aspect (especially the variety show). however, it's clear that Michael outgrew a group setting very early on.
for legacy, i'd choose Jackson 5. they had more career highlights, and made more of an impact.