What are some pros and cons of the Battle of Vicksburg?

The decision to advance down the West bank of the Mississippi was disastrous.

This decision appeared to have been forced on Grant by Lincoln giving secret permission to John McClernand to raise a private army and take it down the river.

Grant should have reminded McClernand that he was in Grant's territory, and ordered them all back to Memphis, to advance through the interior of the state of Mississippi.

Apparently Grant thought this would look too much like a retreat. Sherman reckoned it cost them four months' delay.