I had pretty good service with The Lift House (Ft. Union Blvd & Wasatch Blvd - it's right near the Stop-N-Go right at the entrance of Big Cottonwood Canyon - there's also a stoplight). Most people buy their boots too big, because the liners will pack out. They're also pretty good about boot modifications - punching out the shell, grinding the inside of the shell, etc. Plus at the Lift House you can get discout tickets, $10 off a Snowbird tram lift ticket, and I'm sure they have a combined Alta/Snowbird ticket.
The key to buying new ski boots:
1. Take the liners out of both boots, and get your toes touching the front of the shell, you should have at least two fingers at your heel.
2. Try on lots of boots, and your friend will find one that fits him.
3. Walk around in the boots for somewhere between 5 to 15 minutes, and go outside (it's a lot colder than the shop - typical skiing weather), if they will let you.
4. Narrow your choices down to at least three pair of boots.
Any knowledgable ski shop in Salt Lake, Alta, Snowbird will narrow your friend's choices down and recommend a boot that your friend can live with.