How to decide wich responsive base theme is better for a certain project?
Yes, it really does depend on your needs.  I went through this exercise last year.  These were my considerations.

Since we are a web design/development shop, we needed a base theme that we could potentially use for the majority of future Drupal 7 work.  For Drupal 6, we had been using Zen, but decided to start fresh with D7.

At the time, the decision really boiled down to Omega, Adaptive Theme, and Boron.  From here, I worked out what my dream requirements were (in no particular order):


Uses 960.gs seamlessly
Responsive layouts
As much config as possible via the UI
HTML5 starter templates
Works well with Panels


#1 and #5 are debatable pluses, but were hard requirements.

Something that works well with Context was also nice, but not a hard requirement because we leverage Panels so much.  Mobile integration was not a requirement for us, beyond the response layouts, also due to Panels.

At the time, Omega was the only real match.  960.gs can be added to any base theme, but the UI control over the grid and grid assignments is a huge bonus for us (allows clients and non-technical people to change layout without needed to bug the developers).

Now that we have several Omega-derived sites deployed, I still think we made the right decision and am glad we put a lot of thought into the process.