Stuck between Snow Leopard and Yosemite install-no escape!

[deckeda]

So unless you have a specific application you know isn't yet Yosemite-compatible, I'd keep going and get that instead if you can, or after Mavericks is installed.

Yosemite brings any Mac's functional integration a little closer to iDevices running iOS8. If you do that, do the same with Yosemite's installer.