Having gotten into the .17HMR a couple years ago and being extemely surprised and satisfied with it's accuracy, it is my caliber of choice for target shooting 100m/yds and below. At times, up to 200m/yds. Since my start (with a convered 10/22M), I've increased my collection that are built .17HMR from the start. These include a Marlin 917V, CZ452 Varmint, Anschütz 1517MPR, and an Anschütz 1717D HB. (Also have a second 10/22M on order to convert to .17HMR with slightly higher quality components thant the first gun.) The caliber gives high end .22lr target rifles a run for the money.
Out of the guns listed, IMO, the CZ is the best buy and no brainer in balancing accuracy and cost. Getting 0.50" @ 50yds is not difficult to do with this gun. The only drawbacks are a creepy trigger and, at times (at least mine was), rough bolt travel (which should smooth out with use).
In terms of comparing with .204Rug or other flat shooting lightweight guns, the .17 HMR will get you at least equal the accuracy for a lot less money. You'll get less downrange power and an inability to load to your specs but out to 150-200yds, its pretty hard to get the accuracy the .17HMR achieves for the price.
Can't say much on the .17HM2 as I'm still not converted to that caliber. It is, from what I've read on RimfireCentral quite accurate. It is slightly cheaper than .17HMR but for me, I'm not hurting for funds that would cause me to consider the cost difference. Anything the HM2 can do the HMR can do and more (longer range).
.17HMR : Essentially a .22mag necked down to .17.
.17HM2 : Essentially a .22lr necked down to .17.