I have the B26 in .22 and the B40 in .177. I like them both. If I could have only one, I would take the B26. The B40 is more of a bench gun, as it is a real beast to carry around. About 3 pounds heavier than the B26.
The B40 and B26 are also very similar in power at about 15fpe. The B26 is more ambidextrous (the sporter version, not the B26-2, which ahs the thumb hole.) The B40s comb is not ambidiextrous. It can be used by a lefty, but the comb is sharper on the wrong side. The B40 requires a scope, while the B26 has decent iron sights as well. I have Leapers 3-9x32AO on both rifles.
Also, the break-barrel B26 is a easier and faster to load. Some would argue a break-barrel is safer than a sliding breech loader. I think a B40 is pretty safe compared to a B3 finger eater.
I got my B26 with a full Macari kit and tune. The B40 was deburred and lubed. Both from Mike Melick.
Accuracy wise, the B26 can hit do under 1/2" at 20yards with Beeman FTS, its fave pellet. The B40 is still new so I can't judge yet while she settles. I'm not sure of her fave pellet yet, but she should shoot better than the B26 from the bench. Both are better guns than than I am a shot.
My 2 cents, get the B26 in .22 and let the lust build again for the B40.