Resonator guitars were originally developed so that guitar players could compete with the horns in big bands in terms of volume. They were quite successful in the days before amplification. they were always played like regular guitars in those days. Their use for slide came later. A resonator guitar in good playing condition is quite loud. They may or may not have good sustain.
If you could describe the sound of your resonator guitar as dull there is something wrong with it. Have a luthier check it out. You may or may not like the sound of a resonator guitar but it certainly shouldn't be boring.
A very brief primer:
Besides the two kinds of necks there are also three different resonator configurations each with own unique sound. These are commonly referred to as: National, Dobro, and tricone.
The National type has a cone (like an aluminum speaker cone) with it's center pointing upwards toward the face of the guitar. A disk of wood rests in the center holding the saddle. They have a bright sound and a crisp attack. This is the configuration most popular for bottleneck slide playing. Most of these were made with round necks, however square necks were made also.
The Dobro type has a cone that is folded in the middle so that only the center part of it points toward the face of the guitar.The bridge is a frame that suspends the saddle above the tip of the cone. There is an adjustable screw that connects the cone to the saddle. These have a warmer gound with good sustain. This is the configuration most favored by bluegrass players. These guitars are more likely to have a square neck. although round necks are not uncommon.
The tricone uses three much smaller cones of the National configuration. These are the brightest of the three configurations. Both neck types were used.
There is a lot of info on the web
