Since I've had the pleasure of using both of these keyboards, I wanted to let potential buyers know what to expect.
Realforce
The keyboard is quieter when typing on it. It's also heavier and doesn't creak as much when holding it, unlike the much lighter HHKB. The variable actuation point is also a positive with the software suite that you can download from Realforce. The Windows version works perfectly fine with an Apple computer, including the FN functions such as volume controls. They've even remapped the function keys by default so they perform the same as on a Mac keyboard. It's all done well, and you can even remap the FN key if you want.
The 30g switches on the Realforce were initially jarring to get used to, as I felt that they were a touch lighter than a traditional scissor switch keyboard. They are definitely tactile, but you'd almost not notice it unless you were focusing on it. When bottoming out the switches, it feels mushy, like squishing soft silicone. I can comfortably rest my fingers on the keyboard, but I have to keep a lighter touch than what I'm used to so I don't actuate the buttons. The lightness of the 30g Topre switches means you'll make some mistakes starting out, but you'll get used to it within the first few days. I'll suggest however that if you find the 45g HHKB switches slightly too heavy during long typing sessions, then consider aftermarket options like DES domes. This keyboard is for someone looking for something very light.
HHKB Type S (2 years old)
I haven't needed to remap much of the HHKB as it comes with pre-defined DIP switches on the back that you can change. It's also very good that they give you printed instructions on the back for the functionality of each DIP switch, meaning you can forsake the software if you wanted to. For Mac, it's compatible just as well as the Realforce once you flip the Mac/Windows DIP switch.
As for the 45g Topre switches, they're much more tactile with a stronger initial bump at the top of each press. Bottoming out these switches feels completely different to the 30g Realforce, with a much sharper bottom out feel that doesn't leave you guessing on whether you've hit the bottom. Pressing multiple keys simultaneously creates a resonating/reverberating feeling across the bottom that isn't captured on the Realforce, which makes the Realforce feel more refined but makes the HHKB feel more satisfying, like your every input is being hammered into it and reflected back to you.
