As those other threads Split linked will show, if you’re speaking simply in terms of raw performance, Windows/PC is the current hands-down winner for Cubase.
But really, with modern computers and audio interfaces this really only makes a difference in your day-to-day work if you’ve got projects with dozens of tracks and hundreds of plugins. Otherwise any current-model Mac will be perfectly adequate for most folks’ needs. Tons of professional musicians and producers use Macs. They’re fine.
But at the moment, for a number of reasons, if performance is a big consideration get a PC.