I just ordered a new meter socket from the utility company and it is rated for 200 amps. My friend is a certified electrician and he will be doing all the work. He advised me to get an exterior main breaker so we could relocate the interior sub panel approximately 7 foot away from the point of entry. That panel will eventually be replaced as well. However, I was told to purchase a 150 amp exterior main breaker, as my friend felt like 200 amps was overkill. However, doesn't the exterior main breaker have to be rated for 200 amps since the meter socket is rated for 200 amps? This equipment will be used on a cabin in Michigan and I live in Illinois. In Illinois, I believe the two have to be the same. In any event, I am having difficulty finding anyone who carries a 150 amp exterior main breaker, so I am leaning towards getting a 200 amp breaker. Also, I was advised to purchase No. 1 copper for the runs from the mast to the meter socket and then to the main breaker. That was conditioned on getting a 150 amp main breaker. Does that sizing change by using a 200 amp main breaker?

If you have 2/0 wire, I would go the 200 Amps, 1/0 is good for 150 Amps, Would have to look up for #1, TK probably knows off the top of his head. A 200 amp Socket is the Maximum, you could have a 60 Amp service with a 200 Amp Meter Socket.
150 and 200 amp breaker will both fit in the Disconnect, Disconnect needs to be rated for the amps of the breaker.
I would not pull #1's for a 200 amp service. 2 2/0, 1 1/0 for neutral, and #4 for ground, would be good for 200 amps to Panel.