I posted something similar to this in a post named tournament poker and placing question.
I play a ton of live poker and online poker.
I think the reason for this happening is the same as it was for me.
First you are playing lower buy in ,that in turn equals more tournaments played, if I calculated all the tournaments I have won online verse how many I have won live ,online would far outweigh live cashes.
And although I have cashed alot more online,I probably have made more money on one live cash than all of my online tournaments combined.