First of all I'd say try as many as you can, but off your list there the Nikko is a good place to start, a well known instrument, good optics, easy to learn and operate and plenty available for the right money.
AirArms RN10/EV2 Stock-2007 Big nikko FT Kit
AirArms NJR100 Hawke Airmax SR6 HFT/SFT Kit
Feinwerkbau 600 10 metre
HW77K-zeiler 6-24x44 Work in progress
Webley Vulcan .22 Lovely old relic