which is better is always going to be subjective opinion, and we all know what people say about opinions. They are like @$$holes, everyone has one and they all stink.
The original glacier II is notoriously weak. the second gen. (II+) has that addressed with stronger tubes and gusseting.
The Glacier III is a hybrid front and mid mount unit bringing the best of both worlds in one package. Quick connect, and better weight distribution in combination with the load impact on the middle of the frame where it's better suited to take the load and possible impact. I have not heard ANY complaints about the Glacier III systems.
Don't forget there are many other brands of push tubes out there. You don't have to stick with Polaris. It's my understanding that the blades can be used on just about any push tube system. But I could be wrong. and If I am, I'd just modify it to work. one of the benefits of being able to work with metal. Anyways lets get this train back on the tracks.
I've done a good amount of research into plow systems as I plan on building my own. from this research, I've decided that I'm going to copy the Glacier III system. The quick connect in combination with the minimal ground clearance loss when the plow is not on and the hybrid mount make it the best option in my opinion. Please refer to opening statement about opinions.