I grew up on that flight! DL 767s, 757s, and MD80s from LGA to both FLL and PBI. I live in between.
TWA was my other choice on LGA-PBI. Sadly, that flight has been dropped. TW JFK-PBI was another flight I was on all the time. Same fate as its LGA brother.
Used to do US Airways a lot too, now its Metrojet, haven't been on it since the changeover though.
JetBlue has been great (for last minute).
Never tried Spirit.
Flew CO from EWR several times. Didn't love the schlep out to New Jersey.
Delta Express wasn't bad on FLL-EWR, cheaper than CO. But again, didn't like going out to EWR.
Once flew Midway over RDU. Couldn't say no for the fare.