I've had a look. It can't even be compared. The PSX version doesn't do what the PC version does at all. There is no "right" speed - since the PC version is a unique effect. If you want to go by how fast the PSX version is from the start to a solid colour frame, then it's 100 frames - at 60fps, so around 1.66 seconds. The PC version is 75 frames when at 60fps, which is 1.25 seconds. So with 25 frames more needed, a frame rate of 42 would create 1.66 seconds. Obviously, this is bogus.
As I said, the effect is so different that timing is meaningless. Aali's driver allows customization of the fps regardless. I personally think 60fps works well given that the effect is on screen far more pronounced than the PSX version, which quickly dissolves away to leave a solid colour. Also, using anything other than 30 or 60 will create issues if using a standard monitor of 60hz. The game was designed for 60 to begin with, so that's pretty much what you should use. The only other thing left would be altering how the swirl works somehow - but that's a lot of work for something so trivial. Any real change to the swirl would have to be worthwhile - as in editing it totally to work like PSX version.
If you don't mind the issues it will cause, simply set the frame rate to 45 in the config.