I have done both. Insanity was one if the hardest things physically I have ever done. P90 x was weak. The best thing about p90x is ab ripper x and that it helped me rehab from surgery so I could get back to the steel.
today is bench 3 sets of 5 at 65%,75%, 85% of my max then I will do pull ups and push ups. Might try to get a max on weighted push ups. I havent done a weighted push up in years.
standing barbell press 4 x 8-12
seated dumbell press 3 x 8
rear raises 3 x 8-10
cable side raises 3 x 10
standing calve raises 5 x 12
seated calve raises 2 x 12
I'm getting back in the gym after a layoff. The linear 5x5 has always been my go to routine when getting back in the swing of things.
With that said, yesterday was my second day back and my legs are rocked. Not as sore as i was on Tuesday though. That's the amazing thing about high frequency training. Eventually I will no longer get any real doms on the 5x5.