So you have narrowed down your search for a banjo by figuring out you want a:
5-string banjo (vs. a 4 string or 6 string)
Resonator (as oppose to an openback)
Bell bronze tone ring (not all banjos have tone rings and there are many types)
Now you need to figure out what neck wood you want on your banjo. The two most popular are mahogany or maple.
Maple is a very hard and dense wood. This wood when used on the neck of your banjo will give the instrument a very bright tone. This is generally the preferred neck wood/tone for traditional bluegrass banjoists. This is most likely due to the fact that Earl Scruggs, the king of bluegrass banjo, played a maple banjo and had a very bright tone.
Mahogany is a much less dense wood than maple. When used as the neck wood on your banjo it will give the instrument a much warmer tone than maple. Some feel it is a sweeter tone. Bela Fleck plays a mahogany banjo and gets a very warm tone from his banjo. J.D. Crowe also played a mahogany banjo and was able to get a more bluesy tone.