Yogi Berra had a saying... "When you come to a fork in the road, take it!" In other words, given a choice, take all choices.

A partitioned table would work very nicely here. It combines the benefits of have individual tables for each "customer" along with the benefits of have one huge table for all customers. It makes future archival processes simple, it makes adding new "customers" simple, it makes table maintenance simple, and it makes index maintenance both simple, relatively unobtrusive, and fast.