It is entirely possible that the two sound different. Not likely one is better than the other, but since no small integrated amplifier/DAC can be "perfect", you can't get the best possible performance in all respects, and one may sound better to you than the other.
Your amp uses a technology called DDFA. The concept is about 8 years old (I think), and a lot has been written about it. Here is a link to a paper from one of my favorite brands, NAD, who was an early adopter, and co-developer(?).
http://www.goodwinshighend.com/manufacturers/nad/M2-white-paper-EU-Web.pdf
DDFA has impressive numbers on paper, but this is not "free". It achieves those results essentially by putting the material through another transformation in the digital domain.
Another factor is the USB interface. This amp and some other similar devices have had mixed reviews for their USB implementation. Not
bad reviews, but enough to be a bit cautious (look up the first review on amazon).