The most intriguing thing for me about this instruments is the huge dynamic scale they have, and if you treat them roughly the tone gets sort of an "acoustic distortion".
I play three different models of resonator guitars, that I'd like to introduce to you real quick:
1929 NATIONAL TRIOLIAN (POLYCHROME)
I love the color and the gorgeous patina of this instrument! She sounds wonderfully balanced: very harsh and brittle on one side, but with rich and sweet overtones on the other. She always inspires me every time I pick her up and the tone is always 'on the spot'. She was one of the first 500 pieces of metal bodied Polychromes ever made, with the body consisting of 3 pieces instead of 2.
1930 NATIONAL STYLE O
This was my very first resonator guitar. It's a 12 fret model and the 'smoothest' sounding of all, but also has a real 'wirily' tone - she's a real character! The awesome sand-sprayed hawaiian motives delight me every time I play or look at her.
1956 NATIONAL 1133
These models were originally released as student models, but the sound is really quite unique: it's basically a solid body guitar with a built-in cone, which is smaller than the ones in regular resonator guitars. She is really funky and the sound reminds me of an old kitchen radio somehow... I modified her with an old lipstick pickup, because I plug all my resonators into a valve amp. Since the guitar is so different in sound and playability than others, she always takes me down new musical roads.