Ooh controversial! Seriously I've never seen anything get as much of an unbridled hate bandwagon as Bixby, and I've owned iPhones so have seen my fair share of hate. I think even Jeremy Corbyn is treated more fairly than this one!
There was a bug in the past week or so where you couldn't ask Bixby something like "open Google Play Music and play my cheese playlist" (she'd think it wasn't installed) and you simply couldn't ask anyone about it as all the responses were "lol you use Bixby?! You *****. Turn it off!! Problem solved!"
An update came through today... it's fixed

But already the few others I saw asking about it have been convinced to just install disablers and never use it again.
I use both and play to their strengths rather than see it as some sort of rivalry where one has to be turned off and the other has to "win". Good managers have PAs - great managers have a team
Bixby's strength is in phone settings and anything that deals with the Samsung apps. So things like starting and stopping Samsung Health workouts, taking photos by voice command, setting reminders, turning on wifi calling when you're not too sure where the setting is, etc. What I like is it also shows you on the screen what it's up to. Also the ability to chain commands, or to make an alias like "good morning" that automates a chain of commands without having to say them all.
GA's strengths are in general queries and anything related to what Google might have learned about you (unless you're one of these who thinks Google is some moustache twirling villain who needs to know that you tend to pick up a bottle of water in Tesco on a Tuesday morning so that they can meet you there and suck out your soul for some nefarious scheme, or that overnight the government will turn evil and hack Google's database so they can round up and exterminate anyone who likes tacos, and have therefore turned it all off). Knowing what you're referring to if you say "how's the match going", remembering your shopping list, dealing with Google apps, getting you home when you've had a few too many jagerbombs and are a dribbling mess, etc.
Admittedly I don't get much from the "Bixby Home" thing and have turned that off, the button is remapped to the Android equivalent of alt-tab so I can quickly switch between Pokemon Go and Ingress, but holding the button down still calls Bixby and saying "okay Google" still calls Google.