I believe the Touch may a bit smaller and lighter. I can tell you from past experience, while it is nice to have all the music you own at your finger tips, it can equally become annoying skipping past the ones you do not want to hear. I find my 16GB touch is more than ok for the music I really listen too on a regular basis. I some times rotate music around some, but about 60% of what is on it stay's there.
FWIW the Touch pawns the Archos 5 in SQ, but it DEAS allow carrying all your tunes with you. I'd go w/a Touch>LOD>Amp myself. Screw the Archos if it sounds "meh". Or, just get a Zune, sounds fantastic w/an amp through the HP out.
The Archos 5 has very good SQ (good DAC, amp, and s/n), just as good or better than the Touch. The custom EQ function isn't so great on the Archos, but then again the Touch doesn't even off the feature at all.
As far as the choice of having your whole library available at any time or having to live with a subset (or having to guess what subset you will want to hear in advance and re-loading your player all the time) it's not even a close decision IMO, go with the high-capacity player.
it can equally become annoying skipping past the ones you do not want to hear.
Think, the Archos players have NEVER been known for their SQ, mostly for their video capabilities. They've "improved" the SQ on the Archos 5 & 7, that doesn't mean they sound all that spectacular. Sorry, the Archos players sound like "crap", but they ROCK when it comes to the vids, and browsing the net (the 5 & 7 ONLY). Also, the volume is a bit low, improved from previous generations, but still to low (EU volume crap - but WORLDWIDE!!!).
No way in HELL does the 5 or 7 sound even CLOSE to the Touch!!!