Any taildragger, driven by someone who has an inflated opinion
of his skills and an underestimation of the skills required, is more
likely to groundloop. It's not particularly difficult if the proper
training is given.
The biggest single physical characteristic of an airplane that
has bad groundlooping tendencies would be the main wheels too far
forward of the CG. A close second would be a short tail. Third might be
a narrow main track.

Dan