The movie-era uniforms used in Yesterday's Enterprise looked goofy. They look cheap without the tunics underneath, especially at the neckline. And then they took out the belt, but they still kept the belt loop.
I was having a discussion about this over at Flare Forums. Basically, I surmised that the production spent so much money on the new Enterprise-C model that they didn't have a budget for new 2340's-era intermediate Starfleet uniforms and phasers. So they ultimately used a uniform that was already about 65 years old (Trek-chronologically speaking), and a phaser design that was even older.
The thing is, they could have easily re-used some alien-of-the-week uniforms and weapons for the Ent-C crew. The cool Rutian police uniforms come to mind. Heck, they could even have bought some futuristic-looking water pistols at a dollar store, painted them black, and stuck them onto the belt loop. It's not like the Ent-C crew even used the phasers anyway.
Conversely, they could have used the already-existing Excelsior model as the Enterprise-B instead of the C, and push the date for its disappearance back to say, the 2320's. That way the movie-era uniforms wouldn't have been such a problem; there would have been a lot more time for an Ent-C ship to have been in existence (2320's to 2360's) instead of no
Enterprise at all for the 20 years between the C's destruction and the construction of the D; and best of all, they wouldn't have had to spend any money on a new starship model. Of course then Sela couldn't have existed (or at least she would have been about 20 years older than she was portrayed as).