|Okay, I'm not sure I completely understand your requirements. |
If the "16+16+24" is the number of users in each buliding then your total users is: 56 and a 24 port switch will not provide enough ports.
Second, Cisco isn't the only game in town. If you shop around you'll probably find a good switch that will do everything a cisco does and will cost less initially and also, will cost less to support long run. Also, it will probably be easier to configure.
Having said that, if one of your requirements is routing on the switch then you need a Layer 3 switch. As to which one in particular, I can't see that it really matters as long as it's an L3 switch and you know how to manage and configure it.
In a nutshell you need:
1) To have sufficient ports for the number of users and network capable devices (ie: printers, scanners, etc) that will be connected in each building
2) To be able to route on the switch (again, that's a Layer 3 switch)
3) To be able to configure and manage your switches
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.