...the only thing the B lacks compared to the X is the Speed 3 bank/turn.
Well, that's four maneuvers, and the banks in particular are useful when you're managing an approach (which is what I imagine will be happening most of the time when an opponent engages you with Flechettes). But perhaps it's useful to point out that when I fly X-wings I use R2 Astromechs whenever I can afford them to fix exactly this kind of stress problem--and I certainly never run PTL without an R2.
I don't see a lot of difference between the B and the X, honestly.
Its probably also useful to note that for the last while I've been flying mostly TIE Fighters, Firesprays, and the very occasional Interceptor. In comparison to those, the X-wing does kind of fly like a bantha: it doesn't have the TIE's 1-turn or 3K, both of which I use all the time, and although the Firespray and X-wing have essentially the same dial, the auxiliary arc makes it an entirely different ship on the table.