Is P90x or Insanity workouts really effective.

Yes it does. If you follow the regimen even only 90% you will achieve results. You can also achieve the results without spending that much though. Running, pushups, situps, pull-ups, and proper diet are still the basic building blocks to getting fit. P90x and Insanity are just the latest fad. They are good in that the videos are instructional and motivational to an extent, but if you have that already no need to buy.

I can attest to P90x working, but i'm not sure about the other one.