I'd be skeptical myself of any mechanic that thought a port job that included raising the exhaust port was accomplished by adding base gaskets. And what does that have to do with increasing bottom end, anyway?
Agreed, port work is only as good as the person doing it, and a lot of persons think they know a lot about it. ...and they don't.
I had an RD ported by someone that supposedly knew what they were doing. I expressed my intentions for the job to be a port 'tune up', NOT something that would negatively effect the bottom end response.
I ended up with a bike that wouldn't run under 5+krpm, couldn't pull a 6% grade in 5th gear.
What you're not likely to get is a response from a rider that has had his bike ported that will tell you much of anything. 'Moh better' is a cute descriptive term, but doesn't begin to tell the story of the angles changed, the metal removed and the port reshaping that took place. What's important is that the guy that promises 'moh better' delivers on his promise.
That's where reputation of the person doing the work is crucial.
Which is to say....follow the above advice.