Two very different establishments.
Jellyrolls is in essence a cabaret, featuring two comedians badgering each other and the crowd while pounding out tunes on facing pianos. There really isn't anything at PI quite like it (the closest anything comes is the Comedy Warehouse, which isn't a cabaret format).
Jellyrolls attracts a mix of 20-40 something locals and WDW guests. Has a reputation of being fun but crowded, loud and
very smokey. Being a BWV owner who always stays in BW view viilas, I can also confirm it regularly dumps groups of inebriated visitors onto the Boardwalk at closing. So if you really want to "act like idiots," plan on being there late when you'll have plenty of company.
Atlantic Dance is tougher to generalize about because Disney has never really found an entirely successful format for the place and is thus continually tweaking it.
The original late 1990s vision was for it to be a nostalgia-oriented 1930s-40s themed dance ballroom featuring big bands and swing music. That didn't attract crowds, so it didn't last very long with recorded music becoming the norm with the bands only on weekends.
Band Performing inside Atlantic Dance in November, 2001:
Starting in 2003, Disney went through a short period of turning it in to a Latin music club, aiming at the local non-guest Hispanic market. That also flopped.
Disney then walked completely away from the original ballroom vision, put in a big, ugly music video screen and basically turned AD into a generic disco with live music on weekends (regular live music there finally evaporated about two years ago, and is now only on special occasions such as New Year's Eve). The primary crowd has become local, middle income and Gen y-ish; if you go go there, that's the milieu to anticipate. In essence, Disney has tried (and IMHO failed) to turn it into a poor man's version of Mannequins Dance Palace at PI.
