No, this bag is a better choice!!
Seriously though, I'm not famililar with the size of an XTI with grip or the size of the 24-105. This is what I normally pack that is about the limit of this bag:
MAIN COMPARTMENT:
1. 30D with grip (bag is really not tall enough for 30D+grip, but it will squeeze in there-XTI may fit better, don't know)
2. 70-200 lens
3. 550EX or 580EX flash
SMALL/TOP COMPARTMENT:
1. 17-40 or 17-55 wide angle lens
Like I say, I'm not sure how big the 24-105 is, but unless it's less than about 5", you probably wouldn't fit all those items in this bag.
Hope that helps.