Electromechanical keyboards vs synths

There's something about electromechanical keyboards.  By these I mean such legendary favorites as the Rhodes and Wurlitzer electric pianos, the Hammond organs, and of course I'd be remiss if I didn't mention the Hohner Clavinet.  When they are in good condition, they are a joy to play.  They seem to have a life of their own.  

I have a love for these keyboards, mainly because they seem to maintain a sense of space in a mix.  By comparison, when mixing synth or sampled emulations of the same instruments, I always have to work much harder to make the synths sit into a mix.  Generally short (sub-50 ms) delays are needed to create some sense of ambience.  Not so with the Rhodes or Wurly.

The Rhodes, taken direct has more "space around it" and "depth" than an arguably good (I'd say very good, in fact) sampled Rhodes.  I've tried this with multiple DIs and preamps with built-in DIs, always with the same subjective results.

Why?  I have some theories but I'd love to hear others.  Any ideas?  I'll post some of mine in a future update.