There seems to have been some claim that lithium orotate got into the brain easier but this does not seem to have any basis. I strongly suspect lithium orotate is a scam. You might just as well use carbonate. Neither is stronger nor harder than the other.
I have tried lithium orotate and it clearly affected me negatively. This was at doses way lower than what is normally prescribed. So I would say it is probably quite a bit stronger.