If you must have a .40 and plan to carry it, the mdl 23 is the one. For about a 100 bucks you can buy a .357 Sig barrel for it and have both. The 9mm barrel is rumored to work ok in the 22/23 as well. If maximum versatility is the name of the game, and you have no plans to carry it concealed, then get a mdl 20 ! I'm sure someone makes barrels for it in .40/.357. The mdls 20/21 are a bit large for concealed carry, for my use anyway.
Savage