Format size counts for a lot in terms of image quality, and there isn't really anything that can be done to overcome that, all other things being equal.
As it is, though, all other things aren't equal, and there are some shots that aren't so easy to get with a larger format. In low light, you're probably going to be happier with a grainier small format print made with a fast lens than with medium or large format. Really long lenses aren't as much of an option for medium or large format.
One of the reasons to shoot a few different formats is to find out what each does best and use them as indicated when you can, and figure out how to make what you have work for you when the camera in your hand isn't necessarily the best option for the photo that presents itself at any given moment.