1. speed to grow faster than your competitors and gain a dominant position and marketshare (assuming you'll be able to translate funding into growth of your team and your customers).
2. In certain businesses, the right investors can make introductions that help accelerate your growth.
1. depending on how much you raise, from whom, terms, etc., you'll give up some equity and some level of control (likely a board seat).
2. if you raise VC, you just essentially sold your company. Most VC's are not interested in entrepreneurs who want to successfully but slowly grow a profitable, bootstrapped company. They want (and need - see: portfolio theory) a 25X, 50X or 100X+ return. They don't want to see you make $1M profit on $5M in revenue. If that's interesting to you, stay bootstrapped and profitable.
VC funding is rocket fuel that will either send you to the moon or send you crashing in the ocean. If you want to continue along a profitable, fun, road-trip that you're in control of, I wouldn't raise a round.
For the business, the advantage is the *potential* to grow bigger, faster, and the disadvantage is you're taking on new risk.
The real challenge is to solve for what you want from the business, and -- cheesy though I know it sounds -- from life. Do you want to stop running this company some day? Do you want to pull a decent amount of money from the company for 10 years or go for a larger sum? Are you still interested in running a business like this or do you yearn for a new challenge?
Even then, there are many more options than just raising money or not, and what kind of money from what kind of investor.
Therefore, the first thing is to decide what you want -- which is a sort of CEO-therapy -- and then you solve for the path which maximizes the chance of that path, and also takes some risk/money off the table depending on the situation.