McCarty's with 57/08s are different from McCartys with the older McCarty pickups in several ways that affect the tone, too. Different finishes, different headstock thicknesses, different tuning machines...57/08s sound a bit more vintage, have more clarity, etc.
The 408s on the Paul's guitar sound very different on the neck pickup regardless of whether they're split or not, having more clarity and are a bit closer to single coil because the pickup senses a narrower section of string, than a typical humbucker. The Paul's guitar bridge pickup is also a little more open and closer to a single coil in tone, as opposed to a standard 408 bridge pickup that's a little closer to a standard humbucker when it's not split.
Splitting the coils on either of the McCartys is less close to a true single coil, and there's a volume drop. Splitting the coils on the Paul's guitar will be a lot closer to a true single coil sound, and there isn't a volume drop.
In terms of the character tone, that's a personal thing. YMMV. We all have our preferences.