I've played for years and years (um...over 30 now, yeesh), and on most of my electrics (strats, LP, teles) I've had 9s, because I simply found them easier to bend. But recently I've been playing an Epi Casino with 10s, and a lot of acoustic (with 11s, I guess, maybe 12s), and I find I am causing the notes to go sharp more often than I'd like on my MD Cu24 because it has 9s on it. My co-worker also has a MD Cu24 and swears the 9s are exactly what he wants - maybe he has more finesse than me, or maybe I just play more than him and on other guitars "too much" (I do play a gig every weekend or so, plus band practice and my own noodling in front of the TV).
So I'm considering for my next string change to go to 10s on the Cu24. That is the factory set anyway...
I wonder whether the SE line comes with 9s because those models are targeted more to the beginner/novice guitarist (targeted more, not targeted solely!).