I can see the merits of both viewpoints, and can only offer my own personal opinion. I originally "learned" to fly on a taildragger biplane that was a hand-me-down from my brothers. I say "learned" because after a couple dozen flights, I never really learned to land, despite the fact that it was a pretty docile plane. I always needed an instructor's help.

When I got back into flying after 15+ years out, I bought a well-used Sig Kadet to learn on. After a couple sessions with an instructor both with and without a buddy box, I had soloed. I now feel comfortable to fly completely on my own, and have actually given a little buddy box instruction to family members. I think part of the reason I was able to progress pretty quickly was because I wasn't afraid of crashing the Kadet. I can try new things and I know I can recover from just about any situation. I can work on making my landings smooth, instead of just making it down in one piece. I can also practice a lot of aerobatics that aren't normally associated with a trainer. For example, this weekend, I practiced flying inverted for extended periods of time. I figure if I can fly around inverted with the Kadet, it will be that much easier when I move on to another plane.

I recommend getting one of the ubiquitous ARF trainers, using it all you can, and then selling it to another beginner. Have fun!

-Scott