There are many .45s out there that are not 1911s.
Take a look at a Hk45Compact, if offers the same capacity in a smaller, lighter package that still allows for Cocked and Locked carry.
Of course there's always the Smith & Wesson M&P45 compact and Glock30 that are both smaller and lighter than a 1911 with the same or more capacity. The M&P can also be had with the thumb safety if that is a feature you'd like to retain.
As for the caliber end of things. There's nothing a .45 can do that a .40 can't and that's true the other way around too.
Neither will do the job better than the other but I do find that I like the way .45s shoot better than .40s.