the ISR 4K can be considered in a hybrid status:
they are SW based routers for interfaces on the router, however they have a multiGiga internal fabric to connect to etherswitch modules or to service modules.
However, the Cisco licensing policies make the users to buy performance and boost licenses to use the total capacity of one device.
There are several threads about this issue the need to buy performance and boost licenses to achieve full throughput.
see the router selector for summary info
I am not able to find the licenses info about ISR 4000 in this moment.
Hope to help
So in essence all the routing is software based? unlike a ASR which copies the FIB table to the QFP (hardware)
This is the reason we mainly use 9300 switches etc as they give much better L3 throughput for the money
you can use a multilayer switch instead of a SW based router if you don't need NAT, or as noted by Leo you don't need to use WAN access techonologies like xDSL or LTE / 3G mobile modems
For inter Vlan routing a multilayer switch is much more powerful because it works in hardware and as you noted is not so expensive.
Hope to help
@Giuseppe Larosa wrote:
you can use a multilayer switch instead of a SW based router if you don't need NAT
Catalyst 9300 (and also, maybe, 9400, 9500 & 9600) can/will support NAT: CSCvp78589
my sentence was generally speaking.
Up to now the only multilayer switch with NAT support in hardware was the C6500 /C7600 (C6800).
I don't know how difficult is to implement NAT in a switch TCAM.
if NAT will be supported on switches like C9300 it is an additional reason to choice them.
For sure switches that are proposed as replacement for C6500 like C9400 and C9600 should support NAT.
I have seen a thread sometimes ago of a user complaining about the lack of this feature in first shipment.