I remember someone had said (sorry that I forgot who -- you know who you are though! ) that the 2.3i are quite a bit easier to place, since they're front-ported, and not back ported. The 2.4i are front-and-back ported, so they need more room away from the wall.
As far as the difference in sound between the two...I have no clue, as I haven't heard either.
Worth noting though, is the 'upgrade-itch" factor. $300 more might be worth the peace of mind knowing that...well -- you can't buy anything better in that particular line.