SERVER QUESTIONS RE BASEBOARDS & BMCs

Does anyone know how many baseboards are in a typical server nowadays? I read somewhere that servers now have 4 (versus just 2 in 2014), but not sure this is the norm vs more specialized multi-node servers.

Also does anyone have any opinions on the different BMC vendors? Seems like a Taiwanese one called Aspeed has like 50% or more of the market, but not sure why. Is there a price / quality difference, or is it more inertia?