Since I got 3 Nokia Lumia 521 cell phones for my family, I was satisfied with their features and functionality, according with their price. Sure, the Skype uses the speakerphone so you cannot use it privately and Google Chromecast is not supported. But what about music playback quality through its 3.5 mm headphone jack?
I compared my T-Mobile Nokia 521 (same as AT&T Nokia Lumia 520) in terms of music playback quality with an iPhone 5 as well as a dedicated Sony NWZ-S639F MP3 player. Results were disappointing, albeit hardly surprising.
I used several headphones for the test. I used larger enclosed Creative Aurvana Live! as well as a couple of portable models, including Koss KSC75. I played the same music through all three devices, including Aram Khachaturian, Camille Saint-Saens, John Williams and pop music.
Somewhat surprisingly, Nokia did rather poorly. Especially so with excellent Creative Aurvana Live! With all headphones, the sound lacked dynamic range, was lifeless and had noticeable holes in dynamic range. Instrument separation was bad also.
In contrast, iPhone 5 produced excellent instrument separation, dynamics and frequency response. It did have slightly lower ability than the Sony to drive larger headphones, especially noticeable in the bass region. At the same time, it sounded smoother than Sony, had better instrument separation and was more accurate.
Sony, for its part, although was less than $100 when I bought it 4 years ago, had no issue driving the Creative Aurvana Live! headphones as well as portables. It produced rich bass, dynamic sound and overall was pleasant to use.
The Nokia 510/520 is adequate only if you listen to music non-critically, listen to podcasts or listen in noisy environments where flaws in sound reproduction will not be as noticeable. iPhone is best in most other cases, as long as you don't attach it to large headphones that are difficult to drive and don't expect solid bass. And Sony is very good overall. It does not quite produce the last bit of excellence in the sound department, but comes close. Plus it produces excellent punch in the bass region, even when no equalization is set. And it has a custom graphic equalizer with presets as well.
For me, since I cannot use the iPhone, I will have to carry my Sony MP3 player in addition to the Nokia.