A lot more breweries are changing their fleets from half-barrels to 50 liter kegs as a way to raise their price without raising their price. Keg size decreases but price stays the same. Kind of like how most orange juice is now in a 58 oz instead of a half gallon carton. It's sneaky because many, if not a majority, of bars don't notice the change in volume. It also hurts those of us using halves to some extent because bars believe we're more expensive when, in fact, the price point is the same.
I say use whatever you want (but I'd avoid a mixed fleet of halves and 50ls--what a pain), but be upfront about it.