First, to stir things up a little -
How about this third option:

I don't know about you guys, but I have lots of images lying around, of 
various versions, simply because I am never exactly sure that I didn't leave 
some interesting code in it. Messy, but that's how I am.

Add to this the ad hoc way I get new releases, which are with or w/o new VMs, 
and what you get is a mess.

Solution - enter the loader image. Write once a pretty small specialized image 
that is go at one simple thing - it checks what your platform is, notifies you 
if the latest newest version in the "image update server/mirrors"is different 
than your newest (assuming you're connected), if so downloads it to a new 
appropriately named directory.

Besides that, this image allows you to choose which of your images you want to 
use, and then either
a.) Loads that image instead of itself (is this feasible?).
b.) Creates a script/shortcut/<whatever your plaform calls it> that runs it.

What does this mean for new users? that they d/l a baseline VM with a pretty 
fixed, dependency-free image which is then a d/l + install + version managment 
wizard all in one.

Daniel Vainsencher