It depends which site you use as to whether it can be better than the casino.
Keep in mind that some sites will deliberately increase your odds of winning initially, then dial it back once you become regular. Live online matches can be joined, but these can be faked too.
If you're already winning 'overall' at the casino, then keep playing there.
However the vast majority of people will lose at the casino, no matter what game is their favourite.
You're actually better off finding a less expensive addiction /hobby /pastime.
Also keep in mind, casinos don't like their punters to regularly win. If you really do manage to consistently beat the house, then they will likely make allegations against you of card counting.
Think of how much rent they must pay in maintenance, casino staff of all types, utility bills, taxes, etc. After expending all that, they must still make a profit. If you're taking away from their profit on a regular basis, they will not be happy.