The Canon XM 2 does not do great stills but it is a mid size
very high quality (non-pro) camcorder. For a 3 CDD camcorder ( or indeed any) it has very excellent lowlight abilities.
The Panasonic is much smaller , more portable and although by no means a poor relation of the Canon for PQ, not quite a match for it.
It will do b y far better stills even if its low light abilities are a bit less able: This is only an issue if the games are late evening and as your TRV18 was able this should not be any problem for the Panny.
For your Sons rugby game I imagine portability ( and unitrusiveness) would be a big plus but the Canon has "street cred"
I dont think IMHO that for the fast moving game any of these 2 MiniDV camcorders has an edge although the Canon has a max faster shutter speed and combined with its better low light abilities will give a better PQ in more demanding conditions
Most importantly both are
significantly better camcorders than the Sony TRV 18.
The Canon is a much better camcorder but is it the (better) one for you?
The smaller size and better stills capability may swing if for the Panasonic in that context.
There are always ( reasonably priced and capable) portable digital still cameras to record stills if you decided on the Canon
HTH