Looks like v3 has the heads closer together to be used with meltable supports, does that limit the materials to using with the same temps? I’m new to dual printing and don’t understand all the differences between the 3 dual head taz printheads.
Bought a taz 6 for black friday to add to the fantastic mini. 
You probably want to get the V3. The V2 is too extended out to really get good results. The V3 looks like a much more solid design. But it is new yet so there are few reviews. From what I’ve seen of it though the V3 looks like a better approach in all respects.
Thank You. The Features section on the product page goes into more details as well. I’m going to wait for some reviews and software updates before buying , especially since it’s not part of the BF sale. Gives me time to sell the Mini and learn a little more about dual head printing.
I’ve had mine for a week and am putting it back in the box until the kinks get worked out. It’s not ready for production yet.