I love the sound of a whirling hard drive in an Amiga.. i'm sticking with HD.
While I do like the whirring sound of a hard drive, I find the neatness of an ide flash drive (not a compact flash card with an adapter, no, a real ide flash drive) even more to my liking in old computers like my A1200. Compact, rugged, no noise, fast, reliable: perfect.
When it comes to my daily dose of whirring noises, I'll listen to my server (4 hard drives, several fans). And when I feel really retro, I'm printing a program listing on one of my two matrix printers (9 pins & 24 pins). Now thát's a great sound! :-)
Pretty soon I'll have my perfect compact Amiga sitting here on my desk: an A600 with ACA630, Indivision ECS, A604, Subway and, of course, an 8 GB Transcend IDE flash drive. The most neglected Amiga of all has at last come of age and is now a desirable part of the Amiga family.