Is it the original game plus extra like substance and subsistance?
No, Portable Ops Plus doesn’t have any of the story segments.
I got the original, though it’s quite hard to find, and thought it was totally not worth it. The story is told via animated comics, so it’s missing the whole coolness vibe of the other MGS games. The controls are awful, the screen is too small to see anything useful, and the reliance on the PSP’s terrible analog stick doesn’t help either. Worse, the game concentrates on a Pokemon-style “recruitment” thing which consists of knocking enemies out and dragging them back to your base, which annoyed the crap out of me. I sold it and watched the story on YouTube.
If you want it, get portable ops plus. I played it, like cid said the controls aren’t great. You can switch to the D-pad if the analog stick is that bad. I beat it and sort of liked it, but i’m never going to play it again. If you play the multipayer expect to never get good at it because if you ever get a full game there will be at least two people hacking.