Good point. My problem with Photoshop is that is tries to be too many things at once, in detriment of performance. By the time it takes to start, I already finished the job in PaintShop. ;p
I have always been in a similar position, while I accept Photoshop is a great piece of software, I have always had difficulty in justifying the price when PSP can do all that I want at a very reduced price. I have no doubt whatsoever that Photoshop can do much that PSP can't but the big question for me is am I ever going to need those features. I am however approaching this from the viewpoint of a hobbyist, I would no doubt have a different view if I was earning a living from it.
There is as the history aspect as well in that many, many moons ago, as a teenager, I had an interest in photography, and when scanners came about allowing the digitising of photographs and slides providing photo manipulation in a room that was not only lit but not full of smelly chemicals, I jumped at the opportunity. Hence the reason I have been using PSP for a very long time, back in the day when the only 'layers' I understood were made from cake icing.......come to think of it I haven't moved too far away from that belief. My Poser world started around sixteen years ago, long after my interest in photography, so the continued use of PSP on my renders was a natural progression.