It's not "tougher" - it's just different.
Historically public protest has been policed by lines of cops physically being a barrier and holding people back etc. This worked pretty well until people started actually attacking the cops (i.e. actually punching/kicking, throwing bottles, etc). Then tactics had to be developed to keep a distance (and arrest the violent assailants) ... hence snatch squads and the aggressive surging forward, then falling back a little type tactics. Then violent protesters took to rampaging around the streets, causing serious damage, looting and generally victimising members of the public and businesses, so the police needed to develop tactics to contain such violent mobs intent on mayhem ... hence the containment tactics.
Now everyone who knows better than the police how to police disorder (i.e. everyone who's never had to actually do it ...) don't like that either - so different tactics, of which the use of water cannon is one, are being looked at (this has two advantages - firstly it is a means of maintaining distance / keeping a crowd back, etc. without the need for physical contact (and hence causes less injury on both sides) and secondly, soaking wet protestors tend to get pissed off.
Personally I hope we don't go down that route ... but whilst we have protestors who are intent on violent opposition to any sort of direction and who pysically attack police lines and / or nearby property the police have no other choice (except to simply let the mob do exactly what they want, which I suspect is what a lot of posters here actually want).