(I've only used an etek and a rail)
Ergonomics: reflex rail. Without question. It the UL frame and boy does it feel good.
Smoothness and kick: Reflex Rail. It's a spool. The etek is a poppet. The rail is very smooth and quiet compared to the etek.
Durability and reliability: Etek. It's no secret Planet Eclipse guns are made to last. However, the rail comes metal while the etek is plastic (unless you get the $120 more metal version). So this could go either way.
Ease of maintenance: Etek. It's a poppet, one of their selling points is lower maintenance compared to a spool valve marker. You won't have to maintenance it as much as the reflex.
My choice (and what I ended up going with): Reflex Rail. The smoothness and quietness of the shot blew me away, while the ergonomics sold me. The thing is to die for in the hands. Throw on a dye NT regulator sleeve and a 45 degree hyper3 reg swivel and it only gets more comfortable. About the maintence. If you have the time to play for hours a given day, you have ten minutes to take the gun apart and clean it.
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