If you are talking training a person that has never shot before, as I have with hundreds of youth, I cannot reccommend strongly enough that a good fitting recurve, as long as they can comfortably hold.
The grip with a shelf will be easier for them to hold. The longer the bow the smoother the draw. I like to use a rubber arrow rest that has the little 'hook' in it to help keep the arrow on the rest.
Once you have taught them the basics of stance, hold, nocking, aiming, release and follow through - then you can move onto other styles of bow.
Even if they are bound to go on to training wheels, the techniques learned in traditional shooting form will help them from developing bad habits with other bows.
I love shooting the longbow without a rest more than any other - but I also believe that is a harder technique to master.