Etherium says their brand new programming language (Solidity) is so very, very, very good you will never ever have to change away from it because it can do literally anything.  Ultimate Computer Geek Alan Turing (https://en.wikipedia.org/wiki/Alan_Turing) says so.

Lisk says that may be true, but such a language is pretty darn hard to learn or use, and needs very complicated computers to run it.  

Lisk says use a simple, common language (JavaScript!) and simple, cheap computers ($35 Raspberry Pi 2s!  $9 CHIPs !) to do 99% of what Etherium can do at 1% of the difficulty and 1% of the cost.