It depends on your personal preferences and situation. Here are the high-level pros and cons of each.
Lifestyle Business (aka Bootstrapped Business)
Funded Startup (aka Investor-Backed Business)
By the way, it's possible to grow a bootstrapped business enough to get the attention of investors, then become an investor-backed business. Ryan Carson's Treehouse is perhaps the most well-known example of a company doing that.
Basically, you are trading ownership and control for cash and, hopefully, faster growth. It's like a bank loan, but now the "bank" is involved in your business strategy, has a shared interest in fast growth, but will eventually seek an exit.
If you don't need any outside capital and can grow quickly yourself, however, then you don't need any investors. Paradoxically, that's the best position to be in when trying to raise funding from investors too.