Transactions are cheaper because the network can handle more transactions a second. The reason transactions are faster is because there is more space on the network (generally, not during high ICO times) and thus encourages more miners. Also the barrier to entry for mining Ethereum is lower than Bitcoin which could be another reason the network functions better most days. Don't be fooled though, these technological changes of speed and cheap transactions can be added to any chain, Bitcoin is moving to a side chain for this. Once LN is on and running, you won't be looking to Ethereum for cheap and fast transactions, everybody will be back on Bitcoin imo.