If you take a poll for this the Bitcoin casinos can easily beat your Ethereum casinos, I have not played on Ethereum based casino yet, the Ethereum fees are just outrageous I'm a small player and fees just eat up my allocation, and besides people are more comfortable playing in Bitcoin casinos they are popular and the majority of casinos already have these two coins, so there's really no competition for both coins.
You won't be charged for just interacting with the Ethereum casino, all you need to do is to login using your personal wallet of choice, it's either on browser extension like Metamask or other known Ethereum wallets. It seems there was a misinformation regarding Bitcoin and Ethereum casinos. Though it may vary on the withdrawal process.