PSP 2000/3000/Go has video out, that can display in progressive scan. PS2 versions of Origins and SM has no progressive scan, as i know. Also PSP always has 16:9 aspect ratio, PS2 4:3 (is it important or not - depends on your TV aspect ratio).
Nintendo Wii has bigger resolution than PS2 or PSP and can output SM in nice progressive scan, so it is a lot better. And PSP version of Origins better than PS2 version in my opinion (better way to play Origins - PS Vita phat with perfect crystal clear AMOLED display or PS Vita TV with HDMI connection to TV).
In my experience, the PSP version was far, far superior.
The PS2 port was one of the most frustrating releases in the series for me. I was pretty stoked to have an easy way to play it without the PSP cables and superior graphics. Especially since I have a weird adoration for this game.
The major problem for me was music loops. Most of the ambient music would only play once and quit. Which makes for some incredibly anticlimactic moments sadly (especially the insane industrial music at the end of the game). Anybody who's played these games knows that the music and ambience is by far one of the most important parts of the series.
This happened throughout the game, constantly between two copies of the game. I completely gave up after that.
But over the years, I've heard of some people having the same problem as me and some people having played the PS2 port and had absolutely no issues. So maybe it was just a shitty batch? I have no idea, but I'd really love a reliable copy someday.
Playing the PS2 version is like playing the PSP version but your eyes are closed the entire time you are indoors anywhere because it is, inexplicably, far darker to the point that I found it unplayable. So, I got it on PSP and completed it that way.