Just to add to the opinions... I have an aluminium & M4 Bailout. It is a really nice, lightweight carry with a blade that will step up and perform well... even over it's head, from time to time. I do notice the weight difference between the Alum & the grivory versions, but it's not a bother.
Here's the thing, though... aluminium, like other metal scales, will "ding" if it gets dropped, hit, or scraped just right. Done it. That's personal experience talkin'. For some, like me, this doesn't matter. It just makes the knife "my knife". Other folks can't stand the scars. Grivory, like Noryl and Spyderco's FRN, is extremely tough, flexible, and resilient.
I used to work in a warehouse riding a man-up cherry picker. I've dropped a Spyderco Delica from 15-20 feet in the air onto a concrete warehouse floor more than once. Know what happened to it? The blade popped out a 1/2 inch or so. Nothing else. I picked it up, brushed the dust from the floor off of it, closed it, and went on. There was no evidence on the knife that it had been dropped. These "plastics" that so many folks don't like are like kevlar for the knife frame and blade. In my experience, they absorb impacts better than hard and rigid materials like metal or G10.
So... just something else to consider before you make a choice for a daily carry, "whatever / whenever / wherever" kind of knife.
