Please keep in mind that logic is primarily an audio editor while FL is primarily a senquecer. Also Logic Pro is not currently the indestry standard pro tools is. Not to say that it's not a professional program, but if you don't have the proper hardware to record with than you may be better off with FL.
Not to say that FL is the only sequencer avalible (although it is the easiest to use); Reason, ACID Pro (Bit more geared toward recording/editing), and Cakewalk Kinetic, are some other very powerful sequencers. Sequencers are good if you don't know how to play an instrament or have the hardware to record since you can do everything on the computer.
Logic Pro is an editor, although it does have some loops and midi compatibility, your really wasting your money if you get it just for that. It's really ment for people who record their music and want to editing on what they've recorded. That said it has some very powerful tools for this, but agein is not the only program for it. Other good ones include: Cakewalk Sonar, Adobe Audition, and Pro Tool (current industry standard), and on reflection ACID Pro probably fits more into this catagory.