I was curious and tried to compare my 2 year old flickr account with my 2 day old 500px account :)
First of all, during the last couple days my view count on 500px was way higher than my view count on flickr. To be exact its about 3x more than on Flickr. I also received more comments and faves here.
On the side it's hard to compare those two platforms for me. One reason is the time difference of my membership, the amount of photos on both platforms, the number of "followers" and my own activeness on either site.
However, despite all those facts, I have the general feeling that the community is more active here and more importantly - it is a permanent activity.
Again, this is just a brief impression of a non-professional, hobby photographer - the average user :)
What do you do? Being active on both platforms or switched from one to another? Let me know your thoughts.