I think with having hundreds of slot games, that will make the gamblers can select what slots games they want, so they can directly play on their favorite slot games. People will have different slots games with a different interface to make them feel happy to play on those games. We will not found the same thing between the offline casino and online casino because each casino will have a different interface. But I think some people still use the offline casino to play slots games because they are familiar with the offline slots games than play slots in the online casino.
The biggest variations in slot machines is just the layout, some people prefer furuturistic layouts, others prefer ancient looking ones. But there are other differences too, for example there are usually bigger friendly slot where the minimum bet is fairly low. Also when you get a free starting balance in a casino it's usually just for a few favourite slot games. In the end it's just best to try to various games and choose the ones you like.