I would say go with the Steam version. But then again they all use uplay anyway.
Well apart from a decent amount of countries getting shafted out of the season pass bundled in with the Deluxe edition, the Steam Deluxe + pre-order bonus gets you the most whistles & bells while still coming in under £45/$70 if you're after collectables.
On the other hand it may get wrapped into the Steam holiday sale for maybe 10/20% off, depending on how Scrooge Ubisoft are this year.