Not much difference in the sailing characteristics between most 'double enders' and 'normal' boats. Consider that most of the 'sharp protuberance' you see on 'double enders' are 'style' and not function, then your 'comparison' is more valid.
Advantages with a double ender
.... you cant stow a lot of unneeded useless CRAP in the lazarette.
.... most are 'symmetric hull forms' which means you can heel them over to almost their beam ends and not have much change in 'helm pressure'.
.... if you decide to sail 'backwards' for long distances, you can part-the-waves like Moses did
.... "looks good" and make the boat 'look longer', stylistically.