I have a Gen III PRI, a DD Omega, a YHM Diamond rail, a YHM lightweight, and another I can't remember who made at the moment. They are all good, but the PRI is very light and does a great job of not getting hot/cold. The thing I don't like about it is that the only way I know of to get a full length rail on top of it is to get a Swan Sleeve, and I try to stay away from anything Dickie sells. The Omega is a great rail, but it is pricey like the PRI. It also has an odd cross-section, narrower than it is tall. I like this, but some folks might not. It is definitely a high quality piece, though. The YHM's are nice, but not as nice as the LaRue pieces.
You tend to get what you pay for!