electrum is using external 3rd party blockchain, it is dangerous, i don't get this idea... why to risk security for a little less downloading? 
You aren't really risking security. The worst they can do is show you fake transactions. They CAN'T modify your transactions, they CAN'T steal your coins, they can only make it APPEAR (but not legitimately in the blockchain) that you have a balance which you don't have, or that you have sent coins which you haven't.