Blogs used to be very different 6 years ago. Then, they were more of an extension of your website, and people used them to improve their website's SEO. If you start one now, though, you'd be better off thinking of it as an advertising tool, not as something to improve your website ranking.
So blogs have changed, and social media has REALLY changed a lot. What used to be the greatest (remember myspace?) has died and other sites and apps have moved in. Honestly, I'm lucky I have teenagers, because by the time the media latches onto something as the "next big thing" it's probably already on the decline. I can just ask the people who really use it (the kids) and see what the real story is.
My daughter's yearbook had a section on school polls, and one of them was which social media was their favorite. Instagram and twitter were the favorites, and facebook only got 1.3% of the vote. Think about that. Kids who are growing up today have brains that are physically wired differently from those of the older crowd (anyone over 25.) Because of the number of electronic devices they've grown up with, their brains are literally wired differently. If you want to catch the wave of younger brides who will be getting married in the next 5 years, you'd better take heed of that fact.
With all that said, you have to remember who your customer is.
If you still get a lot of LOCAL traffic from your facebook page (I assume that you're selling cakes locally, not to people in other countries, right?) then you can stick with facebook. If your facebook page isn't doing it for you, and you're trying to capture a younger bridal demographic, you might want to try something that's more visual, like Pinterest or Instagram.
Instagram is great for people who are on their phones all the time, and who work in a visual field. If you have the ability to snap a couple of pretty pictures a day and hashtag the bejeezus out of them, go for it. You only need to do a couple a day, but you should try to be consistent because it moves fast and your photos will be gone from people's feeds in a short time.
Pinterest is good for long-term photo-sharing because the pictures stay there. It's an interesting thing because sometimes you'll put a picture up and it goes nowhere, then six months later it starts getting shared. Pinterest is also starting a "buy it now" feature for certain businesses, where people will be able to buy items directly from the pins. For someone like myself, who sells online too, that's a good feature.
Twitter is more for short, witty posts, but you can also set your other social media to link to it and broadcast your posts from other places. I have my facebook page linked to twitter, so if I post something there it goes on my twitter feed. Then if I have something else I want to put there I can do that too, independently of facebook.
So to really decide which social media platform to use, you should first look and see what the demographics of each one are, and figure out if your time is best spent on one or the other based on where your customers are. Choose one or two and concentrate your effort there, but if you can link a third (like the way I link twitter to facebook) you can do that too with very little effort added.
Kara Buntin owns A Cake To Remember LLC, custom wedding cakes in Richmond VA, and online at www.etsy.com/shop/acaketoremember