I thought I would also thown in my 2 cents worth (though probably the least qualified person of all these posts).
I myself qualified in Scotland via the S/L system around 2.5 yrs ago and I would never go back. It definetely has it's pros and cons though.
Personally I think S/L is a great way to get your qualification .. it gives experience (canopy control, stability, all round good safety awareness) and also teaches you good stable exits (very very useful for later when you may want to leave the plane at under 3k) - in Scotland the poor weather means exits from 2200ft are common enough (never mind aircraft emergencies). The cons are definetely that, for the same jump numbers, you will be trailing your AFF collegues on your relative skills for a while but then you will be ahead on almost every other aspect of skydiving (spotting, jump mastering, canopy control etc etc).
S/L can be a more difficult way to get though the system as you have to get the feel for the air on your own. Without the helping hand of those daring AFF instructors freefall can be 'interesting' to begin with and if you have real problems with stabilty then AFF can be a much easier/safer way to go.
AFF: As said before this is almost a shortcut to skydiving - after all it may take 6 months of S/L progression and AFF can do it in a week - what does that tell you! Unless very careful many students are overconfident (a very bad thing) and careful coaching is definetely needed to drum in the dangers they pose to the others around them.
That said AFF is great for giving you the air skills (if not decent exits) quickly.
Both have their pros and cons but I say go S/L and only convert to AFF if you have problems in freefall - you will gain experience/confidence from it.
Jeff