What are the advantages of having a USB mic over having a XLR, 3.5mm, or 1/4 inch connector? I.e. quality, price, portability. I am looking at recording sound for video and I'm not sure what type connector I should get. No matter what connection, I think I will be recording the sound straight to a computer. One thing about USB mics is that I have to get a long USB cord. Will this lower the sound quality at all?
When it comes to just the connector, the XLR is the best. It is a "pro" audio connector. 1/4" would be second. Stay away from the mini plugs if you can. If you are doing "double system" audio for video, your best bet is a shotgun mic and a separate audio recorder.
The USB mic will be much easier to connect to the computer (no extra cables or equipment needed) and, as a bonus, bypass the notoriously noisy internal sound card.
The only issue you might have with the USB mic is the sound quality, which will be based on the quality of mic and the quality of the D/A converters in the mic itself.
I would recommend finding a couple of USB mics in your price range and checking out some reviews to see if anyone complains about excess noise or poor quality sound. If you can't find a good one, you may need to go with a regular mic with an XLR connector and a USB interface.