He's lying, the WA looks better on a wall, but the KJ works better overall.
With the WA or WE brass tube design, you spend $800 on the gun, then $300 on the internals to get it working to any sort of reliability, $130 a mag if you want cold weather performance, $60 a mag if you want okay mags, and the gun still breaks down every now and then.
With the KJ, you spent $700 on the gun, maybe $140 on internals, $60 a mag for the only mags you can get for it (which happen to be good mags), and the gun never breaks down!
It's cheaper, simpler, more reliable, and better.
There IS a maximum range and accuracy you can attain at a given velocity, and it's attainable by either rifle. It's just less expensive to get there with the KJ