I presently own two M1s. I have had them quite a few years. Super guns. I had a M2 for one season and did not like it nearly as well as the M1. Different stock and trigger guard design on the M2. The M2 trigger guard would rap my knuckles quite often and had cycle problems from time to time with 2 3/4 shells. Comparing the two models, they have a different feel due to the stock design change. My being more used to the M1 has a lot to do with my choice, Keep in mind that the original M1 and SBE are the models that Benelli built its reputation on. Changes to newer models, I dont consider improvements.
Upkeep? My favorite is G96 Gun Treatment. It cleans, lubricates and protects. Hard to beat. CLP is a good choice for a straight lube.