musashi03
HEROW
I'd go with Den-O, for a few reasons. the four forms had main forms had easy access switching, and with each different form came a different fighting style, and the DenGasher was quite versatile, especially considering a few of it's modes had both short range long range capabilities. even when powered-up, he retained some versatility. Climax Form's ability to use any mode of the DenGasher and had Punch, Kick, and Shout Modes. while Liner Form wasn't quite as versatile as the others, the way Ryotaro emulated the four main forms fighting styles changed things up, and the RyuGun could be use as a projectile weapon.
But you've only seen from Den-O to Double.
I don't see how it could be anything but W outside of that little problem of no real defense form (but that's what physics-defying bullets are for!)
Well, Double does have Metal.