If you are referring to the Webley Stingray, either one would be ok. You might also look at the Xocet. Its pretty much the same gun as the Stingray, except theres no safety and the price tag is $60 less.
The quoted velocites are a bit optimistic though. In .22, expect 620 or so, maybe 580 in .25. 620 is more than enough for rats at 20 yards or less. Neither the .22 or .25 is terribly loud, the .25 should be a bit quieter though.