Load times are faster on PS2. That's about it.

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.

Why was my answer removed? Was I inaccurate?

@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.