A4 + OT for me, no question.
Atm i own an AR, A4 and OT. But when i would have to choose the favourite gear to team up i would go for: Machinedrum + Analog Four!
Octatrack on top of that but you spoke from a double act so yeah:
MD + A4 would be the combo i would go for.
Best drummachine ever combined with the really good sounding Analog Four makes up for everything 
If you need more sound variety, you resample the A4 on the MD, tweak it further, layer it. Not as comfortable as on the OT but works too. AR will probably be sold soon so that i can finally get my MD back i had to sell back in the days to get the AR. Biggest mistake i ever made 