Ps2 has an option to run ps1 games at a faster speed, thus decreasing load times, making the run significantly faster. It is however, not a necessity. Running the game on emu runs the same as a ps1 and all digital copies of the game.
@Jumpyluff, your comment held no significance to the question at hand. DezertPenguin8 asked if there was any difference between Ps2 and Ps1(or other systems) for Ape 1. Your answer covered both the game On The Loose, and differences between Ps2 and Psn for Ape 2/3. Neither of which helped answer the question he asked. Now the info you did provide is indeed accurate, but it holds no relevance.
Ape Escape has been released on the PSN store for PS4 and PS5 consoles! With this both platforms have been added, All trophies has been added to category extensions, and a new clarification on rules has also been added.
ANY USE OF THE REWIND FUNCTION AND QUICK SAVE/LOAD DURING A RUN IS STRICTLY
