I had to make that decision... 1520 or 1320...
I decided for the 1320...
I also have and use HTC One max every day, along with my HTC One. But I love WP for its keyboard, games etc.
I wanted something with a big display, I still have my Ativ-S.
I compared the display of my One max to the 1520... The 1520 display really lacks brightness and for the price the viewing angles are lacking.
But on a Phablet the display and the audio are the most important things along with battery life.
Then I looked st the 1320... I mean, for the price the display delivers just fine... It does what I was looking for at reasonable cost.