There was nothing wrong per se with 1.5, to be honest, there's no reason to call this 2nd Edition, it's really more of a general cleanup and streamlining of the 1.5 ruleset. The only 'major' changes are that size rules switched from being based on base size to a size stat, close combat got a defense stat attached to it and they ditched some overcomplicated and useless stuff.
But if you're curious, all the rules are available as a pdf for free, so you can compare for yourself:
http://warzone.prodosgames.com/downloads