Hi Pat,
Glad you are doing well. As you know, I had my right knee replaced mid September 2017. I was going to wait until January, but decided to try riding in December. Took it slow (Kessler SL) the first few days. Only skied 7 and snowboarded 34 days this season, mainly due to snow conditions. I have retired from racing, because I don't think pushing it on a rutted hard course would be a good idea if you are trying to make the knee last for 20 years. Also doing more soft boot carving as it seems to be easier on the knee.
Asked my ortho dr. which would be better, skiing or riding. He said he didn't know because he didn't ski and try out both and see what feels better. I would say that skiing feels the worst, hardboot carving in the middle, and softboot carving the best. Of course riding the snowboard in powder is the very best. Did 2 days cat sking and 3 days snowboarding in BC in March and had a great time.
Good luck with your recovery Pat!