[Azathoth]

Having OWNED both systems.

The Katana takes all of the advantages of the cylinder system. It is in every way superior to the ICS split gearbox. I have never broken a piston or rack with a WE Katana under abusive battery load (12volt / 14.8 lipo). A buddy has 2 years and about 20 cases of BB's through his Katana same cylinder and everything is still good as new (shooting 1.7j). You cannot say that about any other gun. Pistons are a replaceable part in AEGs, and I have yet to see a need to replace a piston on a Katana or PTW unless it was user induced stupidity (manufacturing defect aside, and i have yet to see one in a ptw in nearly 10 years)

The gears are of good enough quality on the Katana, and frankly you can't and shouldn't "upgrade" them because if you do, you fall into the user induced stupidity bracket for creating failures in the system.

The Katana holds the cylinder in place by using the rear take down pin. The hopup still needs a spring or what not to hold the hop against the cylinder for air seal like a AEG.

You can install all of the fancy trigger, motor and electronics onto a Katana and get close to a PTW trigger response, thanks to the high speed gears (stock) and fewer moving parts (PTW cylinder).

The upgraded Katana is superior to any other upgraded AEG because it uses the PTW cylinder, this makes the gun leaps and bounds more reliable and repeatable when shooting. Easy to clean and maintain (5 mins to take out cylinder and clean like PTW.

TL : DR
Katana PROs
Never seen a broken piston aside from user induced stupid
Never seen busted gears aside from user induced stupid
Cheaper than PTW
Better than PTW clones
Easy to maintain and clean
Upgraded, is superior to other upgraded AEGs

Not a PTW, Not 1:1 dimensions, slower trigger response even when upgraded,

A upgraded and tuned Katana (ER Hop etc) will out shoot a stock PTW. A PTW with the hopup mod done CORRECTLY outshoots a Katana.