For a long time, one of my bands' official website was its ReverbNation page. One just used its FaceBook page, which I thought a mistake but it wasn't my call...
My current (although dormant) 'big' project has a website, a FB page, a ReverbNation page, and a profile on SonicBids.
I believe promoters/bookers for larger events may take you more seriously if you have a 'real' website. For sure, you have more control over posting photographs, video of crowds having a good time, audio files and such. If I had to pick only one, it would probably be ReverbNation (at the 'basic' $100/yr level) which gives you mailing list and social media integration and on-demand EPK generation. We need the SonicBid page because there's a big festival that's tied to a promoter that's tied to SonicBids and if you're not there, you're not getting in. So obviously that was a big waste last year, but they've promised to hold over the membership until this year's festival... FB is a bit of a PITA but it's free and lots of people in our target demographic are there. This is key. Know where your customers are, and be there for them.