well, from what i've read, police and military sniper engagements are a completely different kettle of fish
- police tend to be precision head shots from ranges around 100m
- military tend to be centre of mass shots from 600m
the PSG1 is a high precision rifle, the MSG90 shares a lot of its componants and technology, but is considerably lighter (PSG1 8.10kg vs MSG90 6.4kg) - important if you are going to be hefting it through the field for days / weeks on end
plus, it just looks a hell of a lot better, imo
in terms of accuracy, the MSG90 is up there with the SR25 - both at around 3/4 MOA - i cant find stats for the PSG1 but i'd imagine its in the same magnitude
a fixed 10x scope would be awesome for the addon too, as the trouble with variable scopes is that there are more parts to break, not something you want to encourage, so many snipers fit fixed optics...