I also had (and have acquired again) an A600, I swapped an A500Plus for it because:
1) The composite video out was built in, no more wiggling an A520 adaptor to get a decent TV picture, I am surprised that no-one else mentioned that, a small but significant change. Not all TVs back then had scart leads.....
2) The IDE port allowed me to fit a 40Mb laptop drive into my original A600, and my current one has a 4Gb drive. Booting into Workbench from a hard drive was a major plus and Directory Opus made the machine a dream to work with.
3) With a 1Mb expansion and 4Mb fastram card in, it's quite quick, compared to an A500 or a 500Plus.
4) Going to computer clubs was easier, as it was smaller and lighter than an A500. Remember, most of us had to lug a portable TV around as well.
WTF