I have five snares as of this writing. Picking a snare is a little like picking out shoes - there's a bit of thought about the appropriateness, the conditions, the potential for damage - but there's also a fair amount of whim and "how do I feel today" that goes into the choice.
My Guru 13x7 black walnut is usually my go-to choice when I want the very best sounding snare I have, but its value will keep it out of some gigs where I think it might come to some harm.
My Ludwig 14x6.5 Black Magic is my go-to for all the gigs where I want great sound, projection, and cut, especially if I don't want to risk the Guru. It's my go-to loud live gig snare.
My Ludwig 14x5 Standard aluminium snare is a solid choice for recording, or for a gig where I want a high, dry sound evocative of the 80s.
My Ludwig 14x5 Pioneer is extremely versatile and I love taking it on low-volume gigs, but again, as a collector's item I don't take it out very often for gigs.
The Tama 14x6.5 maple snare that came with my Superstar Classics is the snare I will deploy for high-risk situations or if I need a second snare tuned a particular way (it does a deep field drum sound particularly well).
Having said that, I will often stand at the snare drum shelf and muse, "hmm, what mood am I in today?" if I'm going to just play, or play an indoor miked gig where there's not much chance of anything going wrong. All of them sound more than good enough in general applications. Honestly, sometimes I grab a snare just because I know it's tuned the way I want to play that day and none of the others are!