Hi,
From what I can tell (I've owned the Jaeger video but not the COS system) COS is the only one that purports to actually increase strength and velocity. The concept is that by working various decelerator muscles the arm is allowed to throw to its maximum potential, since it now has the strength to keep the shoulder from being injured by a throw of a particular viciousness. The way it is explained is that the body will naturally limit how hard the accelerator muscles are allowed to work based on protecting the rear shoulder from injury. Strengthen the decal muscles and consequently the body will allow the arm to accelerate faster.
Jaeger's system focuses on the acceleration phase of things - forward throws. His band work is for stretching mostly and very little strengthening. The video isn't that expensive, if I recall. The bands are though. The throwing system doesn't really need the video to explain. Many people here could give you the rundown in a short email. Youtube Alan Jaeger and you will find videos that largely explain a lot of his stuff. Drive line, in their weighted ball throwing program has a link to his pre-throwing stretches, which can be done with any thera-bands/tubing.
My suggestion might be, get the COS system, and do that, and either get the Jaeger video, or get up-to-speed via the board, and combine the two elements.
Lantz Wheeler's Core Velocity Belt may be one of your best bets. I don't care so much for the way he is constantly dangling "Inside information" in front of people for yet even MORE money (he seems to want to get very rich off of pitching instruction) but his Core Velocity Belt WORKS, and I think it may be the only thing of his that you really need. It just takes all of the teaching and such right out of pitching. Put it on and go.