So you are complaining that in your mind a free unit is better than one you paid for? You know eventually every ninja is obtainable in a free way right?

When you pay for a ninja you are not paying for a ninja that F2P will never get, but rather to have early access to it. Newer and Newer ninjas will come out that will outclass older ones, its just the progression of this game.

Now to the point of if GNW is better than Sailor, that depends. Sailor hits multiple people with her attack, which is great for spreading poison tai, or for cleaving once she gets buffed up. GNW has that increased health total which is very niche wining strat.