I have a P700 Jr (tricked up with sight-raiser blocks, fore-end shroud, Anschutz rear aperture sight) a P700 aluminium (stock standard) and recently tried out a new Evolution.
The Evolution is lighter and better suited to those of smaller stature than the full-size P700. The sights can be moved sideways on the Evolution (but not on the 700 or 700 Jr) and this may help those who cant their rifles. It shoots beautifully, just like the other two.
The stock on the Evolution lacks some of the adjustments of the 700/700 Jr, but it's fine for most purposes. I don't think they hava special fore-end for benchrest shooting as yet.
If you start on an Evolution, you'll love it. The P700 may feel a tad muzzle-heavy for some. The tricked up 700 Jr (this model no longer made, but you may find one second-hand) is just about perfect in all respects (the cylinder is a couple of inches shorter which helps with the balance). I like the full-size P700 and my 700 Jr, and I see no need to dispose of either for the sake of getting an Evolution. My 700 Jr with accessories is my "go-to" rifle, but I also love the 700.
It's basically a case of what you have is what you'll get used to. Looking through the sights you wouldn't be able to pick one model from the other. It's mostly weight and balance that will feel different.
They are all great and will out-shoot most of us until the proverbial cows come home.
"Cheaper, faster, lighter - pick any two!"