The Realforce offer different keyboards with different weighted keys. You can get a Realforce with either variable weight (35g, 45g, 55g) or you can get it with uniform 55g key weight. The HHKB Pro has uniform 45g weight. Many people have said they think it is ideal (people have modded their Realforce to replicate this). But just like everything with keyboards; again I think it comes down to personal preference. The selling points of the HHKB Pro are the small form factor, unique layout and great looks (and of course the Topre switch). I myself have never tried a Realforce, and I am curious to what model you have? Are you using the 55g uniform version? Maybe this is why it feels more "buttery" to you? I am not sure. I am curious though as I have not heard that before.