16MB RAM vs. 12MB.
"Not such a big deal" is the common response to this one, but
when you get into running aditional apps, the extra RAM is nice to have.
"that just means you can cache a little more song data." is the common response to that one.
Consider your (average) mp3 collection encoded at 192 kbit/s that extra 4MB of ram would bearly cache a mere 3 minutes of music.
Every bit helps. -er, byte, I mean MegaByte.
I know when I start my hunt for a spare unit, it'll be a MkIIa, for sure.