Is there a difference in quality between using a USB microphone and using a conventional microphone through an interface, or does an interface just give you more control over input?
It absolutely makes a difference. You are actually going through an interface either way because the microphone has an A-D (analog to digital) converter inside of it, just like a dedicated interface does. There is also a preamp in there too, allowing the necessary 48 volts of phantom power for a condenser with chargeable plates like the NT1A to work. The rub is that for the price you are paying, a mic with x quality electronics, x quality capsule (the part that captures air vibrations), an x quality preamp, and x quality A-D conversion is jammed into a price that would appeal to a non-professional. I would not recommend the editorskeys package.
High quality converters (and I'm not talking about reference grade, just decent ones) come in interfaces that can cost, at a channel count of four or so, 400-800 dollars. Well-designed mics hover in the same range at the low end (for condensers, at least... dynamics will always be cheaper). On top of that, even entry-level preamps that impart decent openness and presence to the mic are about 300-600 dollars, like the one from ART or the Focusrite ISA One, and those again are at the low end of professional units.
That being said, mic technology hasn't exactly evolved in leaps and bounds since the advent of transistors (quality has just gone up incrementally) so even a "low-quality" mic like the NT1A is actually a piece of equipment in a very mature line of technology, and will suit most non-professional purposes well. "Low-quality" mics stopped sounding like "low-quality" mics a long time ago. Check out the marketing material from Rode... they show how far even their lowest price point can go.
Still, though, an interface is definitely the way to go since you can swap mics, instruments, and signals from iPhones and other things straight into it with no problem. If you are considering entering into audio as a hobby then an interface is a must, and the Scarlett is one of the better entry-level ones.
At the end of the day it is far more important to understand how to record and mix well than to have the best technology around, but the mic and interface are kind of baselines.
One more thing, since you are not going to be using "outboard" equipment, do not forget to use dynamic compression and EQ on your recorded audio for the cleanest, most even sounding results.
The main difference is that a USB microphone is going to act as a single microphone input through your main audio routing while a separate interface will act as an external audio card and provide inputs and outputs. I can't speak to the USB microphones much as I've never used one, but generally going through the default audio mapping for studio-level recording is a bad idea. There's more layers or processing which are not optimized for latency free and noise free audio. If you're on Windows, the Focusrite will go through and ASIO driver, which allows the interface to act as an external sound card. It also has multiple outputs, line level inputs for pianos or guitars, and more inputs for future expansion. Maybe you want to play acoustic guitar and sing at the same time down the road. Two mic inputs might be good for that, yeah?
Really, the only advantage the USB mic might have is that you're paying more for it, so the quality might be higher. But even that isn't always a good identifier. Your abilities as an engineer are going to be much more of a determining factor in the quality of your sound than anything else. I'd definitely take this with a grain of salt, as I'm typically a big proponent of the Scarlet gear anyways, but expandability is always something to consider with new audio equipment.
I looked into buying a USB mic recently, and have a few bits of information that add to the current answers.
- A well-designed USB mic has all the analogue electronics in the head unit. This means hum pickup should not ever be a problem.
- Some of the mics I looked at specified a maximum cable length between mic and computer of 3M. This is too short, as your (acoustically noisy) computer is likely to be in the next room.
- Some of the mics said "only one per computer". This appeared to be a computer performance issue. Have they not heard of stereo??
I ended up buying a matched pair of analogue condenser mics plus a Scarlett interface box. I'm very happy with both.
Theoretically there should be no difference between a USB audio interface and a USB microphone if you used the same components in the mic as in a seperate mic and interface. (USB sends data in packets, Firewire sends it in a stream and so deemed more reliable for professionals)
BUT you will find the professional level stuff is a rack mount audio interface separate from mic. This is probably due to professionals wanting rack mountable, audio interfaces and to not be tied into just 1 particular mic. Engineers design for the biggest markets.
But lets be honest, unless your a professional sound technician / producer it makes little difference as long as you get a good USB mic. If you were to become professional, in all likelihood you would end up going to a studio equipped with the professional level stuff and re-recording all your stuff anyway.
USB microphones are great if you want to sit in front of your laptop computer and record e.g. a podcast. The integral simple "soundcard" is pretty much a utility item, so any quality issues are mostly down to how good the microphone is and how its pickup pattern, sensitivity and "sound" suit your needs. There are cheap USB microphones and quite expensive ones.
If you want to record more than one source at the same time, or if audio latency is an issue, you are probably better off with a traditional setup. But latency isn't "bad" in all circumstances.