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? 
good thing about open source programs is that you can check the codes and see if there is no foul play in it, or if you don't know anything about coding, you can search social networks like here, reddit, or github and be sure that a famous application like Electrum or Multibit will have some people who checked the code beforeand also it is not "a little less downloading" it is the difference between 25 gigabytes of data and 30 megabytes both downloading and having enough disk space for it