At live poker there is much more information accessable. This information can be used by experience and knowledge to adjust your plays properly. The skill edge at live poker therefore is bigger. In contrast to that you lack a lot of those live poker informations playing online. This is compensated and even outdrawn by the many more
hands you can play online in the same time.
So live poker -> more edge for the skilled players -> higher winrate per hand.
Online more hands per time -> higher winrate per hour.
Another thing to point out is variance. Where your winrate/hand is higher at live poker than it is at online poker it becomes much more unlikely to have a losing streak due to variance at live poker compared to online poker.
Live poker is safer and online poker more profitable on average.