He says that the HD release is just a port of the PS2 version but in HD. No, lol. It's a port of the Wii edition upgraded into looking slightly HD. The PS2 version is missing A LOT from the original Gamecube/Wii versions, namely, the number of enemies that appear on screen which is especially noticeable in the beginning village attack and in Mercs mode, and of course the textures and lighting are horrendous compared to the Gamecube version and little graphical details throughout the game like trees blowing in the wind are missing. Just thought i'd point this out.
IKR! Mercenaries mode in the PS2 version is nowhere near as intense as in the other versions, since due to the limitations of the PS2 hardware the game only generates about two-thirds the number of enemies at a time coming at you compared to the original GC version. This makes getting a higher score more difficult because you have to spend a longer time fragging the same number of enemies as normal.
The Gamecube version in Mercenaries mode routinely will have 13-14 enemies (even more in the waterworld map) coming for you, whereas in the PS2 version it's limited to about 8-9. Even the main mode when you are rushed by huge waves of enemies, the PS2 has way less enemies appearing at once as opposed to the GC version.
Also, while the PS2 version still looks nice, it looks like crap compared to the GC version especially whenever you're in a dark environment.