Regarding the 3 standalone interfaces of the 1100 vs the two 5-port switched groups of the 3011, would that difference make any of the two easier to configure?
To clarify and to respond both to this and a later post of yours, the standalone interfaces vs. the switched groups don't constitute a "WAN" vs. "LAN" split. Any port or group of ports can be configured to work however you want.
Any single port that is physically wired to a switch chip in a RouterBoard can be logically broken off from a switch group in order to act as a discrete port, on a port-by-port basis. I imagine that the way that this is handled internally is that the traffic from the discrete ports is tagged somehow (perhaps with a 1Q tag to/from the switch port internally wired to the CPU/SoC), but if you configure a switch port to act as a discrete port, the details of the back-end implementation are hidden away from you, and you can address the port in this configuration as you would any other port. Also, the implementation is good enough that you really lose no features or flexibility when you use a switched port as a discrete port...no broadcast/L2 traffic from one port on the switch will accidentally leak out of another, you can still nest VLANs on such a port (QinQ works great, etc.), each port is assigned its own unique MAC, etc.
There are plusses and minuses to such an implementation, which is why despite the fact that addressing each port individually and treating each one as a separate interface is possible, somebody still might prefer to use a RouterBoard that is not wired up this way (or at least has enough truly discrete interfaces for their purpose(s)).
The "plus" to this arrangement is that if you need several ports to be part of the same L2 broadcast domain, you can have the switch chip forward traffic between those ports at wire speed without bogging down the CPU at all, whereas if you wanted to do the same thing with two truly discrete interfaces and "switch" traffic between them, you would have to make them both members of a bridge, which basically means the CPU/a software process is switching the traffic for you. Having a switch chip in this scenario is more efficient and frees the CPU up to do other things.
The "minus" is that if you are *not* switching between the ports, or if you are but the traffic needs to hit the CPU anyway for further processing or manipulation (MAC filter or MAC nat), then rather than having, say, 5x gigabit interfaces all with a direct path back to the CPU, you instead have 5x ports that all share a single gigabit connection to the CPU, so in essence you have a "port" oversubscription ratio amongst that switch group of 5:1. You will never be able to forward a total of 5Gbit/s of traffic from outside of that switch group to each member port simultaneously; instead, they are sharing 1Gbit/s fabric to the CPU among themselves. (And if they are configured to act as logically discrete ports, and you route traffic from one port in the same physical switch group to another, it will have to leave the switch chip, go to the CPU, and get hairpinned back by the CPU to the same switch chip.)
Also, if there are two switches on a RouterBoard, they cannot forward traffic between each other without going through the CPU, so traffic between each switch chip is limited to 1Gbit/s. You will have to bridge the two master ports of each switch group together if you want all of the ports on the RB to act together as one big switch.
You can see what I am talking about if you consult the block diagrams for the RouterBoard models in question (available at the routerboard.com site).
You should be aware that RouterBoards have two "default" configurations: one that comes preloaded on a router from the factory that sets things up in a relatively sane way (e.g., automatically configures one port as WAN with a DHCP client, and the remaining ports as LAN with a DHCP server, with NAT/masquerade configured by default), and one where there is absolutely no configuration on it whatsoever (no IP addresses, no firewall or NAT rules, no nothing). The stock factory configuration normally sets each member of a switch chip (except one that it might carve out for the WAN interface) to directly switch traffic between each other. But if you wipe out the stock config, by default all switched ports will act as logically discrete interfaces. So you have to pay close attention to whatever base configuration you start with when you go to set it up to work how you want it to work.