What the heck, I'll put on my flameproof underwear and...
The 240 was designed by idealistic former main battle tank makers; you already know all that (tree, what tree?).
Only a few years into production, it was apparent that it was too expensive to make, and due to it's tank-like nature, couldn't command a premium price, even though it's obvious it didn't really have much competiton in a rational marketplace, which unforutnately doesn't, and didn't, exist.
The 700 series was carefully designed to be cheaper to build with more of a "luxury" feel, so it could be sold for more $$$.

Better profit margin.

The 900 was a refinement of the 700, not so much cheaper to build as more expensive to buy; more doo-dads, safety stuff, etc.

Bottom line: The 900 is more comfy, marginally safer, better finished, more aerodynamic, but the doo-dads, fancier trim, etc., etc., etc., are higher maintenance. It all depends on the sturdiness of your butt (sturdier is a + for the 240) and the skill you bring to the $%*!@# refitting of plastic pieces (skill is a + for the 900). IMHO, the 900 is a lot more rationally laid out than the 240 (This is where I hide).
With advancing age comes a less sturdy butt and more skill; I'd go for the 900, myself. Turbo, please.