Best rifle to buy, gas ram, nitro piston or springer??

What kind of money are you talking about spending ? That'll dictate a lot of what's out there . An do you have a particular caliber in mind ?

Whiscombe.

Spring powered. 

You can have high power, or accuracy. The closer you get to one the farther away you get from the other. Pick a rifle that strikes a balance in the middle somewhere and you will be happy. Generally speaking, the heavier the rifle and the lower the power the better it will shoot.

A TX200 in .177 would be a hard one to beat. If that's too heavy, try an HW95. 

As far as magnum powered goes, the only ones I would recommend are the RWS 48 in .22 and a Beeman R1/HW80 in .20 or .22. Going past the power levels of these guns has not been very pleasant in my experiences. These can put out 18fpe or so and still be fairly easy to shoot accurately. Especially the RWS 48 tuned to shoot around 18fpe, it is a sweetheart at that power level.

If it's the best ever the Wiscombe , or so they say ...I've never even seen one , but they start at about 4500$ IF you can locate one . Pure accuracy's winner would be a FWB 300 for sure but it's not a hot rod by any means , . The TX200, HW 95 , 30,35,and 97 are all winners along with the two newer Walter LGU, LGV . If the words " Magnum" or such wording is attached to a spring rifle cross it off your list . While they can be shot fairly well after a LOT of practice . You can Tak a much milder rifle and shoot circles around one . The only really powerful springer that to me qualified as accurate is a Diana 54 or 56 but they take work and parts to live up to their potential...Least that my 2c
https://www.krale-schietsport.nl/en/walther-lgv-master-pro.html. If I bought a new springer today it would be this one .

I know a guy who has several Whiscombes. They're incredible examples of the gunsmith's art, but heavy and very complicated to cock and load. If you want to hunt and will do much walking I suggest a breakbarrel like the HW95/R9, RWS 34, or a BSA Lightning. If weight is not a factor, an underlever like the HW97 or TX200. I prefer a breakbarrel for hunting in case I need a follow up shot due the their ease of loading, underlevers are more fiddly and slow to reload.

About 75% of my shooting is with springers, and I have tried many. The stable now consists of an R7, R1k and a pro sport, all in .177. 

If I could just keep one, it would be the pro sport, currently tuned to 12fpe. The TX200 is very similar to the pro sport. 

From my experience, springer accuracy goes downhill fast when you exceed 15-16fpe, and is optimal at about 12fpe. 

No interest in gas rams. Too fussy, and IMHO steel springs do everything better at a fraction of the cost.

R

@Mexcomp, check out these three recent topics. Most of your questions will be answered there;

http://www.airgunnation.com/topic/need-your-springer-advice/
http://www.airgunnation.com/topic/most-accurate-springer-poll/
http://www.airgunnation.com/topic/what-is-a-magnum-air-gun/

But long story short, get a Feinwerkbau (FWB) 300S.

http://www.airgunnation.com/topic/fwb-300-found-a-new-home/
http://www.airgunnation.com/topic/fwb-300s-restoration-project-from-written-off-to-brand-spanking-new/

Theoben made a well regarded gas ram if you can find one. I forgot what they called it.