Our new ISP is going to provide either the Cisco 4331 or 2901 as the edge router. It was difficult to find an apples-to-apples comparison but from some reading online it sounds like the 4000 series replaces the 2900 series, however the throughput on the 2901 is much higher than the 4331. Any recommendations on which is the better option? It will be managed by the ISP so not a huge deal but curious if there's an obvious choice here.
Yes the 2900 series will be EOL at some stage, which doesnt mean you shouldnt use them, just that at some stage there will be no more support/software development on them. I would personally go for the 4331 for that reason. If you think that does not have the throughput required. you can go up, but $$ might then be a consideration and you might need to fall back to the 2900 series for monetary reasons. so the answer, as always is; it depends
Performance should not be an issue.
As of 16.7.1 you can unlock the ISR4000 series performance shapers with a Boost license.
With Boost license 4321, 4331 and 4351, all will have a throughput up to 2Gbps+