I dont think that Aluminum frames vs. Steel is quite the issue it used to be. There are many well known brands that have aluminum recievers that have performed well with few issues. I have 5 Sigs, they are all aluminum recievers and I've shot the heck out of all of them.
The steel will take more abuse in the long run, but really, how many of us are really going to shoot a gun enough to wear it out ? If one looks at a carry gun and the percentage that it is carried, vs. the percentage it is actually shot, I think that comfort and concealability become the major issue. Or course being able to hit the target with what you've got is a consideration, but fact of the matter is that most guns are capable of better accuracy then their owners are capable of making them perform.
What the aluminum framed gun WILL DO, is let you carry it for longer periods of time than the same gun in a steel frame. The issue here is comfort. If its too much of a chore to carry a steel framed gun then you wont carry it....and if you leave it home the one time you need it it wont matter how much it weighed.