Out of the two, get the Sightron.
However, you should take a serious look at the Clearidge RM 3x-9x-32. Although I haven't personally seen this scope, it appears to have very high quality optics and ideal features for a rimfire, including an AO. Although this scope can be used for big game, given that it has an AO, you can easily use it for a rimfire.
On my CZ 452 American in .22LR, I ordered a similar scope from Weaver from Jon at the opticzone. It's a great scope. However, next rimfire rifle I get, I am going to definately get the clearidge RM scope. I was going to buy it for my .22, but back then, it wasn't yet available.
Zachary