I guess my main scale is 1/48, though I build a lot of 1/32 as well (love the presence a 1/32 subject has, as well as the opportunities for detail). I have several 1/72 kits, but they're all bombers.
My recommendation? Figure out your ideal "display box". Something where going bigger would really take some consideration. Then figure out which scale fits that sweet spot best. And remember you can always scale up or down for special subjects at will.
Mine is about 15"x15". That's enough to swallow almost every 1/72 kit (minus something like the B-36 or B-52). It's enough to swallow the majority of 1/48 kits, minus the big craft like B-17s or PBYs and up. And it's enough to swallow a good number of 1/32 WWII single-engines (a 1/32 Jug has a 15" wingspan).
On the Bench: 1/32 Trumpeter P-47 | 1/32 Hasegawa Bf 109G | 1/144 Eduard MiG-21MF x2
On Deck: 1/350 HMS Dreadnought
Blog/Completed Builds: doogsmodels.com