Actually, the Bridgestone S-11 will give you the best mileage and is a better tire than was ever available back in the day. Very good value also. Can't go wrong with the BT-45 either, but mileage will be less.
Mileage for the S11 seems to be in the 7500-plus range. The BT45s will get about 5000 miles for the rear one. You can typically wear out 2 rears to one front, if you are not picky about razor-sharp handling (if any CBX can be called that!). For all the more miles we put on these things, either tire is good. I've used both with good results.
4500 to 5K for the rears and double that for the front . . . . but most of those miles are pretty . . . . agressive riding, at rallies and such - Hard on the brakes into the corners and as much wide open throttle as the roads would allow. If you were just . . . . commuting I think the tires should go a bit farther
If you like to ride it hard, I'd recommend the 45's as the extra grip will come in handy. If not, the 11's because the extra mileage will be nice