MK7
12
It’s all about what you want
you don’t really need one. Lol, “even if I’m not planning to use samples”… that one would be a reason to contact your girlfriend.
When watching all those youtube videos, you should have a look at how often people touch their machines. With more than 2 machines, it’s usually not more than a mute here and there. Even Dataline usually focuses on one machine at a time and the others are passively playing in the background. What do you need a hub for? Are you going to create a playback show? 
A4+AR will be totally sufficient for all you need, without knowing what kind of music you make. If you want to make a “reasonable” decision, buy an Akai MPX8 for just 100 bucks to add additional samples here and there. Crossfader transitions can be replaced by other transitions, so that isn’t a really reason either.
Btw, I focused on MD+A4 for gigs so far, great couple!
My OT can replace MD+A4 on stage. Playing all three at once doesn’t make sense to me except having more lights flashing and more gear to carry.
If you want one, buy one.
EDIT: As a side note, I think that the OT is THE techno machine! However, MD&A4 also, and AR for sure! 