CZ 550's are heavy in most chamberings, but my FS in 9.3X62 is just right. It is a great shooter; the bolt was rough but smoothed up fairly quickly with use; I plan on keeping it forever. I had a CZ527 in .223 it was very smooth and fairly accurate, but I didn't shoot it very well offhand and I wanted a faster rifling twist, so I traded it.
I haven't shot a recent M70 but they feel nice and look good. I would make my choice depending on cartridge and the feel of the individual rifle.
Had one of those 550 'Mediums' in 9,3x62 with Mannlicher stock. I traded that "boulder" for Remington 660 in .350. I could not be happier with this swap. If the 550 was the one with black polymer stock and 23" barrel I would probably have kept the rifle. The difference from FS to that one is as great as night and day.
The CZ is great for Mini-Mauser .22lr or cavernous rounds like .416 Rigby, .450 Rigby,.... that require magnum action for everything else there are better choices out there.
