Although I've not owned any Snells, I've got to agree with John--I've never heard a Snell (pre-Boston Acoustics) that didn't sound great.
I have heard, and really liked, the E/III but not in comparison with the D. The E was very well made, very coherent, and fun to listen to. My suspicion is that they tend to work better with good solid state--that is when I've heard them sound their best.
So I'd say you're unlikely to go wrong with either one.
Best,
Bob