Dumb question, but I know nothing about .17 rimfires and I know I'll get more that statistics here (like weighted opinions).

"Twenty Two Long Rifle", "Twenty Two Magnum".
They both shoot for the most part a 17 grain Hornady V-Max (the HMR is available with 20 grainers), the HMR clocks 2,535ish in my CZ 452 and my 452 .17M2 does just at 2,000ish with the same projectile.
For me (weather permitting) the HMR is a 185 to possibly 200 yard gopher rifle and the M2 is 125 to 150ish tops.
I stocked up on Hornady HMR at $7.42 a box and did the same with the CCI M2 at $2.99 a box (probably never see either price again).
For what I do I have a use for both of em.
That's my take

the 17 hmr is a rimfire made on a 22 mag case. the 17 mach II is a centerfire made on a 221 case

oops my bad i was thinking of a march v1 - the mach 2 is on a 22 stinger case