By downloading another app you also get the advantage of not using Google and not having your data mined for advertising/the service randomly cancelled on a whim.

Instead, you are simply giving it to another company when Google probably already has a lot of information. Even if they start out not taking any more information than they need to (which, being a money app, probably is a decent amount of information), I don't trust any company to stay this way.

Other companies shut down and sell off to larger places too, so you aren't exactly off the hook there. Slews of apps have done this. You are simply aware of some of googles' stoppages, in no small part because you might have used a couple or because they get publicity for longer.

Google has a lot of opt out controls to prevent personalized advertising. Other services are doing a lot worse. Google Pay is instant when using a debit/credit card and has great support. Setup is a breeze so even if it is canceled one day, which there is no indication of it happening soon, you really aren't losing anything.

Leave now and avoid the rush when they cancel it

So what if it is cancelled one day? You lose like a few minutes of your time and then complain that no one else offers something as good?

In the long run? I’d expect so.

What's the difference at that point?

Yes.