I'm not sure that Bella would have been better off with Charlie as her primary guardian, but I do think it could have made her a different person character-wise. Obviously, since we see it in the books, she turned out okay having lived with Renee most of her life. I think, because Renee had the tendency to be "scatterbrained," it caused Bella to grow up a little faster and become much more mature than most people her age. Perhaps, had Charlie been the primary guardian of Bella, she wouldn't have had to worry so much about that. I know she cooks and cleans for Charlie in the books, but I think if Charlie had custody of Bella when she was younger, he would have been forced to learn those things himself in order to take care of her. Plus, she would have been growing up in Forks which is a pretty small town and might have fit in a little more as she grew up.