Well, this one's pretty much the same as Robots VS. Zombies. Of course the maps are a little different, there's a tiny amount of new items and there's the Last Stand mode.
Sadly the new maps are not spectacular at all. There's nothing new. Not at all. There's just a mapping and that's it. Put in some new energy fields, lava, acid traps, bridges, random events, whatever. Same goes for the items and skills. The skills are exactly the same as far as I saw and the approximately two new items don't make a difference at all compared to the 2011 game.
Even the mech's model's still the same. Other graphic enhancements where not to be found either.
Also the Last Stand mode is soooo extremely easy. I started it with the default items and default two towers (minigun and laser) and made it to level 100 without any problem or any monster touching the cores. Same goes for the normal maps by the way. They're so easy, you can't lose, if you're not some total incompetent idiot.
Another contra would be the health system. Why's there health in the first place? Monsters will never ever attack the hero (mech). You just occassionally lose some health if you're walking past the electric fields, which is rarely the case as I didn't have to move at all during the entire game.
And finally: The player still can't walk through, if you build the towers too close to each other. That's pretty damn stupid, because there are enemies which are five times bigger than me and just walk through this tiny space between the towers.
That's about it. I really liked the 2011 version, but you didn't change ANYTHING. There's no improvements at all. It seems you're just uploading the same game again and again, while your grammar and spelling are getting worse.