Imagine I need to provide a router to connect to:
Port fa0/1 (10Mbps)
Port fa0/0 (100Mbs)
Port e1/0 (10Mbps)
in addition, I need to connect this router to a 10Mbps MPLS circuit.
Which router model should I consider? I thought about the 3825, but it seems the 2821 can do the job as well?
How about 2851?
Either of the 2800 series routers you've mentioned can support your two FE ports, E1 and 10Mbps MPLS.
You don't necessarily need the extra power the 3825 provides to accomplish that.
Please see the following link for 2800 series comparisons: