I really can't imagine not buying a truck (or any other item, really) that I liked because it was a specific brand. Makes no sense to me. Do companies pay some of you to drive their stuff? They don't pay me, so I buy what I like and want to own ...
The GMs are great trucks. I bet the Silverado rides very nice, has smooth power, and the best transmission in the business.
It won't have the room of your Megacab, though, that's for sure. About the only thing I didn't like about my '06 was the size of the rear seat -- it could have used a few more inches of leg room.
Good luck!