hmm.
are you saying that a big box which can house hard drives will collect less dust than a small box that can house drives?
i haven't used the new computer yet but as far as i can gather, it will collect less dust than the old model.. probably a lot less- even if you have a separate hd enclosure as well
i think it's important to point out (well, it's something that should be completely obvious but i guess it needs highlighted) that internal expansion in no way means free expansion.. you're both paying for it as well as providing space and an enclosure etc.. on most levels, there's absolutely zero difference between putting a hard drive inside a box and putting a hard drive inside a box.
Dude, are you kidding? You think there is NO difference between plugging an internal hard drive directly to a mobo vs having to buy an external thunderbolt chassis and cable? Have you looked at prices? It costs about 25 cents to hook up an internal hard drive via a SATA cable and the included power supply hookup.
How much is JUST a thunderbolt cable?