Do the 9 ports on the rb493 qualify as being between 8 & 24 ports?
If 9 ports are enough you could also try to find a rb564 daughterboard and use it with a rb600, that will give you 3 gigabit ports & 6 10/100 ports. Personaly I do not trust Mikrotik's 'switch chip' on the rb192 that might also be on the rb493, I have seen lower speeds on a rb192 vs a rb150 router. I need to double check the performance running the latest RouterOS though.
If you need more ports and you need a rb4xxAH model, then use a nice managed switch + router. Then you can use any router you want without worry about having enough ports. Or an even better solution is two routers running VRRP
connected to the switch for redundancy.
I agree that a nice managed switch is a better switch than a router configured to do bridging. Mikrotik bridges do have the host table, and you can look up addresses and which port the connect to.
/interface bridge host print where mac-address=00:0C:42:29:24:5C
But a switch can give you more detailed port stats and they do faster 'switching', some even do cut-through switching instead of store and forward switching.
A switch is an extra point of failure at remote tower sites for some ISPs. A managed switch with 12-24 ports normally has 1-3 fans that can clog up with dust and use more power. Using MikroTik we have migrated to using routers at each tower, some towers still need a switch for extra ports. But where we can, we have a router with enough ports for everything to plug into. We have deployed almost every model of multiport routerboard, rb153, rb150, rb192, rb532+rb564, rb600+rb564, rb450 & x86 + 2-3 r44 cards for 8-12 10/100 ports. At our headquarters we have a few x86 routers with 8-16 ports to migrate away from HP Procurve & Cisco switches for our wireless backhauls since we now 'route' to the towers instead of bridge.
We still use switches at our headquarters for PCs & Servers as we need quite a few ports, some running gigabit. But for our routing infastructure to our towers we use routers. We also use the multiport routers at the base of our towers to do OSPF routing & PPPoE to our clients.