Is there any source of information that compile the nuances of different consulting firms? 

So far I can gather below information (might be wrong and/or incomplete in some cases). I understand that it's gonna be almost impossible to do all firms' nuances, but the firms listed below can be the scope.  

McKinsey: often regarded as the best, great network, great mentorship, strong in pretty much anything 

BCG: more 'posh' than McKinsey, strong in innovation, digital, among others 

Bain: amazing culture, pragmatic delivery, strong in PE 

Kearney: often regarded as the leader of tier 2 

Oliver Wyman: strong in financial and PE, good culture 

Roland Berger: strong in auto industry, strong in Europe, but so-so in America 

Simon Kucher: leader in pricing strategy, strong in marketing, though having limited presence 

Strategy&: still having the Booz vibe and reputation, though PwC's name is kinda weaken the brand?  

Monitor Deloitte: was strong as Monitor, not as strong under Deloitte 

Alvarez&Marsal: having more while collar vibes compared to all above, trying to climb the ladder 

EY Parthenon: still confused with EY as the parent