Well... let me think about it. The thing is, I've got some games that were released on other consoles, too. Like the Valis series, Winds of Thunder, Gradius I/II and Salamander. However, I've only played them on the Turbo so far, and that's why I can only judge by reviews that the Turbo versions of these games are seen often as the better ports.
In case of the Gradius and Salamander games, I would like to give the original Arcade versions a try. But I fear that these would be way too tough for me, since the console ports usually let me choose the difficulty.
EDIT: Now that I just won Salamander Deluxe for PS1 in an ebay auction, I'll definitely give the Arcade original a try.
Although I wanted that game mainly for Salamander 2.