Newbie to the forum... but I'd like to throw my oar into the pool. I did S/L and it took me quite a long while to get to intermediate (A licence) level. I'm still relatively inexperienced, but I think I can safely say that whichever course you choose, the most important thing to remember is that once you qualify, you are only just beginning to learn how to be a skydiver! The course just lets you start the real learning process...
The way I see it, some of the bigger benefits for me of doing the S/L course were:
1. It (generally) takes longer which may seem an odd pro to have, but you would be surprised at how much you learn from NOT skydiving all the time (e.g. packing, just general knowledge garnered from conversations with instructors and others, extreme patience ;), etc).
2. Lower amounts of money spent each time but over a much prolonged period - I probably spent just as much as an AFF student altogether, but I couldn't afford the high outlay over a short time that an AFF would have required.
3. You aren't scared of getting out low... when they eventually do it, that 5 000ft level for some AFFs is pretty scary for them as the ground suddenly looks so much biiiiggger than it did from 13k!
4. If you need to do a hop 'n' pop from 3 000ft, it isn't going to be a problem and you will have the "perfect" arch for it that an AFF student might not.
5. Your (effectively) doing it all for yourself which means you don't have the potential for developing an attitude of "it's OK if I don't pull, the instructor will get it for me..." - you learn the attitude of "if in doubt, get it out" instead.
Personally, if you've never done a skydive before, there are no benefits to the "but AFF is straight from 13k" line of thinking... it is all going to be amazing to you. A 3 second delay from 4k is probably going to be as mind blowingly exciting as a 50s freefall from 13k; the first time you see the horizon while free-falling is just as amazing as anything you'll experience in a 50s free-fall from 13k; etc. That is, it is all good no matter which way you do it!
The biggest downsides are:
1. You will get stuck on at least one level and it can take a lot more to get off that level than it would if you had an instructor with you all the way like in AFF.
2. It takes an awful lot of patience and determination to stick it out. If you do S/L don't expect to see 90% of the people who did the same course as you ever again... they will inevitably give up after one, two or even ten jumps due to a lack of either.
There are other pros and cons, but they are the biggest ones in my experience.
Anyway, enjoy it however you choose to start... -----
Official 100 jump wonder