I'm currently working my way through the King IFR series. I used their VHS tapes to pass the written in the mid-90's.
With several companies offering online or DVD programs, the advice boiled down to this: there are two main options, Sporty's and King, and it depends on whether you like the King's style. People have complained that John King tells cornball jokes, and they hate that, so they prefer Sporty's. Others point out that a lot of IFR knowledge material is inherently dry, and John tries hard to keep it from getting too boring by cracking his jokes. Sporty's IFR videos have the reputation of being a bit...dry.
My suggestion? Watch a couple of the demo videos on the King site. If you like their personalities, go that way. If you can't stand them, go Sporty's.
For me it's kind of interesting to watch them age, because some of the material hasn't changed and they use older recordings, and then you have recent stuff in the program as well.