[knubbe]

From the reviews, the Pros seem to be more refined. They listened to the complaints about the originals and fixed the fit and cable issues, and tightened up and extended the sound in both directions slightly. I have not actually heard either so take it with a grain of salt. If you can find a place to demo either version it's worth it.

 

[Azathoth]

Sennheiser IE8, end of discussion! You can adjust the quantity of bass the way you like it.

 

[jjb3]

I have owned the Bose IEs and UE 5EBs and the EBs have greater detail and are less muddy. They are clear, but require at least 50hrs burn in before the bass really starts to get detail. At first it is muddy and bloated, but then the upper bass tightens up with a nice background of deeper, resonant bass. The 5EBs are a good step up from the Bose.