I've already got the PSX version of Abe's Oddysee, any differences or added value that might make me wanna get the GOG version?

None, ive played through both.
Only thing the pc version does better is the load times... but thats so very minor with a game like this.

What about controls? I think it is much easier to use the numbers to communicate rather than a combination of buttons.
Also you get loads of awesome stuff if you get the GOG version, if that kinda thing matters to you :D.

I use logitech dual anolog pad, virtually identical to the PS one sooo..... ummmm... yeah, no difference there :P
However, speaking would definately be easier on keyboard... now i feel stupid for not thinking of that! >_>