I find most SIP apps, unless they're extremely buggy, for basic operation are pretty similar other than differences involving UI. And a lot of them don't support push. Those that don't, including Bria, at one point, had reps raising security concerns. And then, suddenly, Bria offered push with a subscription, which I found laughable, to be honest. There was this ongoing rant by a Bria rep, and then suddenly that thread was deleted.
I can say that when I was testing Bria with push on someone else's iPhone that push notifications were coming in more slowly than with Groundwire, but that could be due to any number of reasons including push server location, routing to the push server, and where I happened to be testing from. I should also state that I've been stuck with iPhones (yeah, yeah) for some time now, and I haven't done a ton of testing with Groundwire on Android.
I can also afford $13.49+tax a year (which is the annual subscription fee for Bria). I simply refuse to pay for something, if I don't have to, on an ongoing basis.