this is the beatin dead horsey, but you can allways go here;
http://www.rimfirecentral.com/forums/
http://www.varmintal.com/17hmr.htm
http://www.chuckhawks.com/index2l_rimfire.htm
Basically, out to 80 yards, the 22 mag has more energy, past that the 17 is better in all ways
you can make honest to goodness 200 yd shots in a calm wind, it is faster than a 22 mag at the muzzle, with it at 100 yds, with a 100 yds zero, and scope sitting about 2 inches high/centerline, the 17hmr only rises .5 inch at 50 yards, and is only down about 3 inches at 150 yds, and down about 8 inches at 200 yds. So it is a smokin round. It moves less in the wind, and has more energy out to all effective ranges , after 80 yards, than a 22 mag. It is also very apparent, that except for the occasional fluke, it is far more accurate than a 22 mag.
now it is expensive, but so is the 22 mag now. Which is why I am totally geeked out over the 17 mach 2. it does for the 22lr, what the hmr does for the 22 mag. Plus it is 4 to 5 bucks a box, so it is plink-worthy.
Plus with the mach 2, you can also fire 17 Aguila or pmc round.