"What is the best guitar mic for the home studio?" Unfortunately, it's a really bad question. Here's a better one: "What is best guitar mic for my guitars?"
This is at least a step in the right direction, although no-one can answer it for you. Here's the real answer: the "best" guitar mic for your guitar is the one that's the best match.
Guitars are infinitely unique
One thing that's so cool about playing a guitar is that every guitar is unique. Each guitar has its own sonic characteristics that make it stand out from the rest. That's why you can have similar bands with similar instrumentation and musical styles that at the same time are clearly distinguishable – all because the guitar is what separates them. From clean to crunch, dark and smooth, to light and bright, there are seemingly infinite guitar sounds out there, and all of them different. Which means not every mic will capture them perfectly.
Every microphone has its own EQ curve
What's important to note (and this may be obvious to most) is that every microphone on the planet has its own EQ curve built in. We call this frequency response, but in essence, no matter how flat the microphone spec sheet says it is, each mic imparts its own EQ on the audio that feeds it. So, much like presets on an EQ plugin are kind of pointless because they don't know the frequencies you're feeding them, blindly saying one mic is the "perfect" guitar mic is just silly without knowing what guitar it's supposed to capture.
The secret is in the perfect combination
In the end, all we're trying to do is capture a killer guitar tone. We want it to sound exactly as we hear it in the real world – only even better! The secret, then, is not in just picking a good mic, but rather the right mic for the guitar. One that's a good match.
If you have a bright acoustic guitar, for example, many of the typical condensers might be a bit too harsh for it, (since many of them have a slight top end bump). A better match might be a darker, warmer tube microphone that rolls off the top end, or even a ribbon or dynamic mic.
The opposite would be true with a round, warm, and dark sounding electric hollow-body guitar, or perhaps a nylon string classical. Without a bright mic to "open it up," it might not cut through the mix enough. In this case, the brighter mic would be the "perfect" guitar mic in many of those cases. It's all about finding the right combo of mic-to-guitar.
The simple two-mic test
Now, if we had all the microphones and all the time in the world, I'm sure we could discover the absolute best match of a mic to the guitar in question. But who has the money or time for that?! Let's take a more minimalistic approach and do a simple two-mic test.
To do this test, all you need are two mics – that sound different. This could be a condenser and a dynamic. Or perhaps two condensers that simply have different frequency responses. Whether you have to rent or borrow a mic, or maybe sell something to buy a new one, just get a second mic (assuming you only have one) so you can do this test.
Set up both mics on stands right next to each other, running into two of the preamps on your interface. They should be the exact same preamp. Then, simply create and arm two mono audio tracks in your DAW, each labeled according to the mics, and hit record – letting your chosen guitar play through a verse and a chorus of the song.
Go back to your DAW, level match the different guitar tracks, and solo back and forth. Which sounds better? Which one complements the guitar the best? You'll likely favor one mic over the other. Once you do, you've nailed a good match for that guitar sound. Done.
If that's all you did, you'd be steps ahead
I know that test sounds simple and obvious, but have you done it? Or do you simply reach for your most expensive (or coolest looking) mic and hit record?
You see, if all you did was a simple two-mic test, you'd be in great shape because of two things:
(1). You picked a mic that better complements the guitar you're using rather than blindly putting a mic up.
(2). You've learned something about that mic and that guitar for future reference.
This simple test (on each session) can help you learn your gear and learn different guitar sounds better – which will help you get to the perfect guitar mic match quicker the next time.
Then, when you go to mix, you'll be confident about your mic choice, and your guitar will sound better before you do any processing in the DAW.