Evening Call will get you more alcohol for your money and the extra shots are mixed in as they pour the slush. Fat Tuesday puts the extra shot in a test tube, so you can't really add it until you've already had some of your drink and tends to make more of a mess. You also don't benefit from generous bartenders like you would at Evening Call.
Flavors are pretty good, really sweet so hard to drink too much if you're planning on sipping all day but not bad if you just go once.