I have one of the original Model A guns, and the new ones sound even better.
Being recoil operated, Coonan's will handle lead bullets just fine (hard cast, just like any other autoloader, of course). Desert Eagles are gas operated and lead bullets are a BIG mistake for them.
Don't know about the new ones, but I have a set of rubber grips for mine, and they make a huge difference in the feel of the gun for me. The slick wood grips were not to my liking.
One word of warning, don't use Blazer (or any other aluminum cased ammo) in the Coonan. IT won't work well, and may tear cases.
One of the new ones is on my list, but it looks like it will be a while....
All else being equal (and it almost never is) bigger bullets tend to work better.