Here are some comparisons- they're actually quite similar. Both reach really low- Duoza has more impact and quantity of bass. Puro is a more neutral in this region but isn't lacking by any means. One of my favorite things about the Puros is their mid/sub bass- they're roughly equal in quantity but are tuned in such a way they do not obstruct the midrange at all. Vocals shine through like you'd expect from a mid-centric sound but with the large stage of a v-shaped one. Duoza's mids are more upfront as the stage is deeper than it is high but the amount of details delivered are comparable to the IEM500. One of the things I was hoping for the most when I got the Puro was that it had a taller stage- I was not disappointed. Not only is it taller but I think it might also be vented since compared to the Duoza it sounds more open and has slightly lower isolation. Timbre on both are very good. Also worth noting is build quality on the Duoza is much better- I was hoping the knurled body was metal but it is painted plastic...then again they're only $50.
I really enjoy these 'phones- both are great purchases. If you have to choose it boils down to is whether or not you prefer the larger stage and a more balanced, natural signature of the Puro or an intimate, slightly warmer presentation and more low frequency presence of the Duoza.
