I've always played 15" & 17" crashes, originally K Custom Dark 15" and a 17" Paiste Signature, but now 15" & 17" A Custom ReZo's (See - someone likes them!).
For the majority of gigs I play, they're plenty loud enough for your typical pub-gig. Occasionally at larger venues I could have larger, but I like the quick decay of smaller cymbals too.
I'd consider adding a 19" to the mix so can shift up a couple of inches if needed.
I also play 13" K Custom Dark / Z Custom hi-hats, but actually don't really like them for the same reason I like the smaller crashes - they're not washy enough for me. It seems the market agrees as they're hard to sell!
Got an old 17" Zildjian A Thin crash and a newer 15" Zildjian K Custom Fast crash as my *go-to* crashes, but smack my 10" Zildjian K Splash quite often too. The 19" Zildjian A Medium crash pretty much sits unplayed. It's a hoss that needs to be pounded to get it to open up and then it hums and vibrates for minutes. Inaudible (to me anyway!) sympathetics vibrate the snare wires off and on for almost a minute. For most playing, I don't need as much volume, so the smaller crashes suit me fine.