I would say that it's fairly evenly split between 10's 12's and 15's, entirely dependent on each player's personal; tastes and needs.
Each cabinet/driver was designed to a specific target, looking back to our most popular cabinets and then using that as a guide to where we would have gone based on today's tastes, had the technology and drivers been available then. We didn't intentionally "recreate the past", but took the past as a starting point, as inspiration.
As an example, it's no secret that the EVM-15L is one of my favorite drivers, as is the JBL 2220 and even the 2220 series, but these drivers have limited power handling and low frequency extension that's necessary to be viable today. The 2225 has better low frequency extension and power handling but suffers in the high end extension. These drivers also perform better in larger cabinets, but that goes against what (many) players are looking for. The Subway 115 is voiced around these types of drivers but with adjustments made to tune well in a smaller cabinet with acceptable extension, have a smooth high frequency extension with similar off axis extension of the JBL drivers, high broadband sensitivity and it had to be lighter weight than those drivers. It's a delicate balancing of the various variables to develop a driver that works like this, not perfect/ideal at all these demands, but more than acceptable. It's the OVERALL solution that makes a speaker a good choice for the largest number of players possible, but not trying to please every player.