If there is so very little difference between good standard inkjets and their more expensive photo-brothers, I think the same way, about software.
It depends on the skill and tenacity of the "author" using the software. If someone is truly comfortable and experienced with something that costs say £50, then he would be mad to spend £350 for software which in his hands will not bring a six times improvement.
I use Corel Photopaint because it was bundled with an upgrade of CorelDrw which I am very used to using. I then forced myself away from MicroGrfX Picture Publisher to help with file transfer problems.
My entire experience of Digital Photography has been with Photopaint and I feel I know the app. well by now........ I think Photoshop is probably better, but only to the experienced. Paint Shop Pro and Irfanview could be all that the casual user needs, good results, no fuss and quick to use.
Like all "Art" the result is mostly subjective, and the better for not having to think too hard about HOW to do it.