I disagree with your supposition that you're worse off due to the total WS going up from 212 to 263. The reason is that the bulk of that increase in your total is coming from the Shareable block, and you only pay the memory cost for that shareable block once.
So it really depends how many sessions/instances you have running of your app, as that once off 56MB is effectively shared between all sessions.
So the trade off goes like this:
Per session saving from Private WS = 86.3 - 81.9 = 4.4MB (= S)
Per session increase from Shareable = 56 / num sessions (= I)
So you what you want is for S > I. Obviously for low session counts you are worse off, and for high session counts you are better off. So to find the point at which you are equivalent:
4.4 = 56 / num sessions
Gives: Num sessions = 13
So on average if you have more than 13 instances of your app running on a server then you are better off using NGEN.