Personally, I think raking and SPP'ing are both very important skills that should be learned as a beginner. However, to become a good lockpicker, it is always a good idea to focus mainly on SPP'ing, since SPP'ing really helps you understand what goes on in a lock when you pick it, meaning that you learn more about locks and how they react to picking. Also, there are many times when a lock cannot be raked open, due to either the presence of security pins, or nasty bittings (i.e: 700700). SPP'ing as a beginner helps you develop the knowledge of how it feels when a pin is set, and when it is close to opening. This will help a lot, as when you become more and more of an advanced picker, SPP'ing will become more and more useful when you begin to pick more challenging locks. In addition, lock picking is a skill that requires much patience. When you SPP a lock, it takes time and patience, since you are attacking the lock one pin at a time, unlike raking, where you are trying to set as many pins at the same time as possible to open the lock quickly. In conclusion, SPP'ing has its advantages over raking as a beginner, since unlike raking, SPP'ing teaches you how a lock should feel when you are picking it, and really trains your patience. However, at the same time, raking can be very useful too, and should be learned and practiced as well, since sometimes, when you need to get in to a lock in a hurry, or when a lock is too stubborn to SPP open, raking can become very useful!
