Hi, ATD - I don't have much to add to what Dan and Pierre have said, but you might be interested in my "journey" with the fiddle.   What must be now about 5 years back, I picked up a cheap acoustic - just because I thought it would be fun to learn.  [ I have played guitar - both acoustic and electric - for more years than I care to remember, so I had a "basic" if not theoretical understanding of music, what constitutes a scale (the whole, whole, half - tone sequence etc) and to a fair extent key signatures. ]  So, I spent about 4 months "messing" with the instrument - picking out tunes in simple keys like G A D and C on occasion - but the instrument was a horrid thing - it hooted and howled - and although in retrospect I know I could have maybe done something to kill the wolf that lived within the instrument - I really just wanted to play music, not undertake luthier work.  So it was put to one side for a number of years.

Around the end of March this year, I decided to get back into it, and bought a cheap EV (and joined the FM community!).  For three months, that's all I used.  Having no actual body resonances to speak of, and little - compared to the acoustic - string-to-string resonances (although they are detectable) - I found the EV real useful for honing my intonation and bowing.  Without amplification, and without effects, sure, I agree with Pierre, and I describe the plain EV sound as "sterile".  It lacks the richness, the overtones, the soundbox resonances and so on.  But, for me, I found it a real good starting point.  It got both my finger positioning and bowing pretty much under control - without the "aural distraction" of sympathetic resonances (and the howling wolf that was my original acoustic).

I then REALLY wanted to go back to the acoustic - and I tried the old fiddle I had - my original feelings from 5 years back were justified - sure - I could pick out tunes - but the instrument just sounded horrible.  I put it down again, and ordered an FM Concert, which I received early July - and after what is now 2 months I feel "really comfortable" with the acoustic (and swap between playing both, quite happily).  Dan nailed it - the acoustic has a much wider dynamic range, it is much more "sensitive" to my bowing action, it has the wonderful resonances (string to string, and those specific to the sound-box) which make the instrument an absolute joy to play un-accompanied.

I still like the EV - and it can be nice to use even simple FX on it, a nice echo, or reverb "lifts it" from its mundane, somewhat un-inspiring sound - and I will usually play the EV against some form of backing track, where I'm maybe just improvising a piece, or inventing some kind of "fill-in" to an existing piece of music.  And - when I mention FX here - I' not even using an external FX box - simple stuff like echo, reverb and other things - can all be done after the event with freeware programs such as Audacity (there are others!) - not much use for live performances though.

Anyway, I can't really answer your question as to which would be "best" to learn on (I personally can't choose because they both brought different things to the party so to speak) - these were just my own experiences during what, in total, is still less than one full year of playing - I feel my exposure to the EV "worked" for me - but I always knew I wanted to return to the acoustic although I had to re-learn / re-educate my bowing action and pressure.    I do have one small point to make - when I say I have a cheap EV - it is indeed cheap - it was under $70 - and OK - I replaced the cheese-wire-like strings, disassembled the electronics enclosure to track down an annoying mechanical rattle - but that's easy to do compared to trying to adjust an acoustic.  I regard that as a small price to pay for what it brought-to-the-party-that-is-my-learning-experience.  

Bill