Go with Whale...it's the best out there
The best y-valves have a robust handle and a "barrel" inside that rotates to line up with all the holes...Jabsco y-valves have a flimsy "gate" that the handle swings to block the outgoing holes...even a grape seed can jam it. Ajustable hose fittings sound like a good idea, but are actually pretty useless...not really needed if you choose the location for the y-valve carefully. Your friend just hasn't had any problems with his YET, 'cuz I've never met one that didn't leak after a few years. And it costs as much as a Whale.
However this whole discussion is moot because all the Great Lakes--US and CN--are "no discharge," which makes it illegal to dump a tank or flush a toilet directly overboard. In fact, you're at least 700 miles from any waters where you can dump a tank or flush directly overboard....so you don't have any need for a y-valve unless you plan to use it illegally, which can cost you BIG bucks if you're caught doing it, especially in CN waters, 'cuz they enforce it more diligently than we do.