Dave, I'd encourage you to find a seminar that isolates the IS fundamentals from any form—or at least any long form—so that you're sure to get the core information. Then you can learn any form and apply the core information from the beginning. If you learn the form first, you have to revise it once you do learn the core information.
Mike, Dan and Minoru Akuzawa all teach those kinds of seminars, but Mike may present the purest basic principles with only the barest of form to bother with. Once you work from pure principles, you can be sure to build all your forms well.
I'd rather spend a weekend doing the silk reeling only, if they taught the core principles clearly, than to spend the same weekend learning the 18 step form in the other video. Learning all that form would probably not leave time to learn the inner workings of each part of the form, so it would be less useful, I believe.
Best to you.