Ollin boards is sort of the "premium" seller in my opinion. Enertion is bigger and cheaper, but I've seen too many photos and heard to many nightmare tech support stories to spend more than $50 with them. On the other hand, Ollin has repaired my VESC twice, and even offered to repair it a third because of a broken capacitor. At this point I should note that I most likely wouldn't have needed 2 of those repairs if I hadn't decided to put the battery connector on backwards…
The price is about $70 cheaper for Enertion's model- but it's discontinued now that they have the vesc-x. Their new vesc is the same price as Ollin's "classic" vesc. If you haven't already heard, Vedder is supposed to be working on a 6.0 vesc (not the vesc-x, that is enertion's own product) that has integrated RF for controllers, bug fixes, etc. If I were you, I would hold off as long as possible until Vedder's new model launches. Some of the sellers like Ollin or even Enertion might pick up on it and drop their prices.
EDIT: The VESC-X and the 6.0 are the same. It looks like exertion sells the single board as of now, while vedder is working on a sandwich board to add NRF and stuff. Again, further developments will clarify...