This is very hard to answer properly without a lot more info, so I'll only tell you what my experience is.
I have a dual-boot system and a crazy-fast one at that (2x1.8Ghz MDD).
In OS9 you only get to use one CPU anyway 80% of the time - there are only a few apps that can use two.
As far as MIDI, nothing but nothing is better, faster, stronger (lol) than SVP and a Studio 4 or 5. Not even close.
BUT, you pay a price: No VSTi support. If that's a big deal for you, you need either OSX or a different DAW.
I get around that by (A) sometimes using an external VSTi host and (B) sometimes exporting tracks to Logic OSX and back.
SVP digital audio performance is excellent as well when supported by a good interface.
Now……
In more years than I like to admit, I have had no/none/zero issues with "latency" and "jitter" using MIDI.
MIDI, like everything else in this world, has limits and one must understand and work within them.
That means that piling on excessive aftertouch and continuous controllers on every track when they're not even needed will cause problems.
I suspect many folks who obsess over jitter would also argue for hours about what kind of $100/ft. speaker wire is the best.
Also…
Re: That missing info: If you're just starting out, picking the best DAW to use is critical. IF, however, you're already a comfortable SVP user, changing horses to an entirely new one is a big deal. The way you succeed at being a musician/engineer/producer is to be as familiar and comfortable with your electronics and software as you are with your instrument(s). Every minute you're interrupting your creativity to search through menus and/or manuals to see if you can make your tools do what you want is a minute you're not creating anything and worse, breaking the creative roll you were on that you now have to get back to. That shit gets tiring and depressing real quick.