Last weekend I was able to try a 1301 Comp, a 1301 Comp Pro & a Versamax back-to-back.
I'll focus mostly on my impressions around the Comp Pro:
Lifter remains "raised" during loading operations. This is a definite benefit during loading, but you can also mod the Comp lifter to do this.
Loading port. Not bad at all, but I would recommend this being opened forwards more. Loading deuces, approx 50% of the time the second cartridge got hung up on a lip - this would need fixing for me.
Stock with recoil mitigation and comfort enhancements, probably the biggest change from the Comp. In short - it works in reducing the recoil at the cost of *slightly* increased muzzle flip. For me, the trade off of flip vs. recoil would be worth it.
If I already had a Comp, would I chop it in for a Comp Pro? That's a tough call but probably not. You are looking at a 50% increase in cost (UK prices) for maybe a 15% increase in performance.
And the Versamax had less recoil & flip than either the Comp or the Comp Pro.