I also use the Stylo as a daily phone. I gave my Zmax to my girlfriend. Nothing beats the battery of the Zmax! It's the one thing I miss the most, especially when we go on our little vacations and we are out for most of the day.
But yes, the Stylo is a very nice phone as well. I don't believe it is all that much better than the Zmax, but very similar in scope and specs. I think the Stylo has a more stylish appearance over the Zmax, with the same screen specs in a smaller size. But when it comes down to the nuts and bolts they are nearly identical. Yes, the Stylo has 5.1.1, Band 12, and VoLTE out of the box, but at least the Zmax finally got its long overdue update to enable Band 12 and VoLTE, which were much needed and the main reason I got the phone in the first place. The Stylo also has the cool stylus and better front and rear cameras. But when it comes to daily use both are about equal.
So I say the Zmax has great battery life and the Stylo has some better cameras and a built in stylus. Most everything is about the same between the two.
And because the Zmax is still in our family I still visits these forums. It's a Tmo version but I flashed the new B13 Metro stock rom for my girlfriend. We both moved to MetroPCS, me from T-mobile and she from Boost. It's still working great, though she looks like she is holding a tablet to her head when she is on the phone. lol It's WAY better than her last phone (LG Volt) so she it very happy!