i don't think that people who play online gambling spend more money than people who play offline, because that is related to the person's psychology, not whether he plays online or offline. if basically a person cannot control themselves when playing, whether they play offline or online, they will still spend a lot of money on the games they play.
Offline or online, I really do feel like no one is more risky than the other or have have a high gambling rate that the other, let's use the offline for instance, you see people who take cash into a bet shop, most of them are not computer literates like the pool you find out it's more older people that go there and most of the times you see them studying the past results of games that have been played so many years ago and for the others they believe the want to be seeing the persons that will pay them physically so no stories if they win a game.
Those who play online are mostly the younger generation and persons who are computer inclined and still do have self respect so as they don't want to be seen by the public that they always go into a bet shop but one big disadvantage of online gambling is that you can easily transfer money from your bank account to whichever gambling platform you deal with and that makes it very easy for you to spend more.
None is better or worse its just good that an individual have self control over it, why most people keep loosing a lot is because they believe magic can happen for them and they just get lucky.