Yes, you have to buy them separately. I had to do that as the Mk19e was only available with the G260 or the D420, and I wanted S560s (as I had standardized on S600 compatible seconds).Can I get the MK19 with a C370? SP site only has the MK11/C370. Will my lds let me combine them or buy online?
Anyways performance wise they are near identical. TBH most balanced regs that aren't Apeks or Poseidon breath within pretty similarly, with only small differences that you can only notice if you are really paying attention. Even between the vaunted Mk25 (of which I own 5) and other balanced regs.
Really the only difference is service related. Scubapros are harder to service yourself with both the kits and manuals locked behind limited distribution agreements in the US. But there are shops to service them nearly everywhere, so if you need something serviced today you have a greater chance of that happening with SP. OTOH Deep 6 provides kits, manuals, and even training very regularly. But has a very limited local service network.