Considering only new grand pianos that I just walked into piano shops and played, here the listing of my perceived action stiffness on average -- from "ligthest" to "heaviest" :
1. August Foerster, Bosendorfer
2. Yamaha
3. K. Kawai
4. Steinway
5. Shigeru Kawai
6. Mason and Hamlin
[EDIT: On 2004 May 10, I played six more Mason and Hamlins in the Mason and Hamlin factory and noticed that the touch on the new M&H pianos felt lighter. So now I move the M&H to somewhere between Steinway and Shigeru.]
There are variabilities from sample to sample, for sure. And, yes, a good technician can change the feel of the touch, can make the touch feels lighter or heavier. Even voicing can change your perception of the touch, tough only to a lesser degree.