Transactions on ethereum get processed from the mempool in order of who wants to pay the most gas to have their stuff processed.

And yes, ethereum has more potential for problems, it's a much more complicated system than bitcoin. Their current goals are proof of stake (getting away from energy wasting mining) and scalability. Bitcoin is great for what it's great for, being digital gold, but it's pretty far from replacing Visa, ethereum actually has a shot at that.