This article is from the Aerobics Fitness FAQ, by email@example.com (Robles) with numerous contributions by others.
Neither is actually "better". All exercise accessories
have their uses. Weights require more muscles in use to
maintain proper form, while the bands and tubes are easier
to use in targeting specific muscles. Bands and tubes also
have the advantage of being somewhat adjustable in
resistance just by changing length. To change weights in
dumbbells, you either need another set of dumbbells, or extra
plates for those which use plates. Dumbbells, however, do offer
a much greater range of available weights, particularly at the high
end, making them more useful in strength training. Bands
and tubes are generally used in resistance training exercises.