If you get outside funding, you lose control. Steve Jobs was kicked out of Apple Computer company which he founded, because it went public and sold stock and all stockholders are then owners for their shares. The board of directors, which represents the shareholders, basically fired Jobs (sidelined him I think, and he quit).
So if Steve Jobs can be fired, anyone can.
However, depending on what you want, it can be fine. Steve Jobs did have billions of dollars when it went public. Nothing wrong with cashing out, if that's what someone wanted to do. Probably without funding, 99% sure he would never have turned Apple into the huge success it is today...the most valuable company in the world.
Nobody can see the future, and maybe your $15,000 MRR goes down to $200 MRR in a year, who knows? Maybe it goes up to $30,000 in a year, who knows? Maybe if you get a VC, it goes up to $10 million MRR. Maybe they sell it to Facebook (or whomever) for $1 billion, and you wind up with $300 million, and Facebook tries to run it a year and shuts it down. Maybe the VCs just tank it after a year because they suck. Maybe with VCs, you will grow great and without them, someone bigger company will swoop in and complete hard and take all your future prospects because they market hard.. Maybe, maybe, maybe. There are a thousand scenarios.
The other thing is that taking off like a rocket ship to the stratosphere is completely different set of skills than what you are doing now, which I don't know if you have the skills to transition from where you are now to what is required to grow like hell. Maybe you might have to hire 240 people a year, 20 people a month, onboard them, fire some, know what kind of benefits to give, manage them, get a CFO because now you're making millions per month and you have to stay on top of that, you have to have meetings all the time with the VCs and other people who have nothing to do with the day-to-day running of the company, publicity, press, all kinds of stuff like that. It goes on-and-on. And to be sure, some people can do that, Zuckerberg as one example. But can you, that's the question.
Personally, personally, I would never use a VC-type thing, because fuck them. There might be a few good VCs, but there's a zillion VCs, and they all are different. Depending on the VC, they can either be hands-off or they can be up your ass every week wanting to know how their investment is going, and everything in between. They might make you go in a different direction than your vision is, just because they think what they think is better than what you think, which 100% it is NOT. Only one out of a hundred investments make money for VCs, so they don't know crap about what will work and what won't. They just play the statistics - 99 bad investments, and one that makes a billion dollars to cover the bad investments. This is how it is.
I think that if a company has a high margin product, then getting VC money is not good. You can bootstrap if you have high margins. If you have low margins product, then you need investers.
Good luck to you.