Xwis is more active than CNC in QM, the last qm match on CNC is 99 minutes ago according to the stats page
The people that play on CnCnet are playing the same players anyways in private FFG games, Xwis is still good activity if you want to do 1-3 series depends on the timezone
As of this post, Ra2 XWIS has a total of 101 users in QM ladder, CNCNet Ladder has 272.
Ra2 QM has 3 players above 100 games played according to stats. The next are few are not even close at 67.
CNCNet QM has 2 guys, just glancing at the ladder, over 230 games played, and multiple others with over 100 games played. (edit: They have 8 over the 100 makr, and most notably, one guy with 380 games)
The "Last QM played" is a very decieving stat that you mentioned, however, I'd argue also favors CNCNet QM greatly. Ever tried getting a QM on ra2 xwis during the off times? My bet is that there could be 6++ hours that go by without a QM played there.
While points are not a 1:1 ratio, the clear rank 1 winner is on CNCNet QM with 1611 points in 88 games played while ra2 has a rank 1 of 51 games played and 613 points.
I'm not sure how one could make a sensible argument for activity that is pro-XWIS. It's just not possible.