I think Facebook gives you more opportunities, and it is more straightforward. Twitter needs much more engagement, but if you have some money, you can buy tweets from celebrities and pay them to mention your product in their tweets. But, for a beginner, I would start with facebook and learn about and practice tweeting for marketing purposes.
Depends on what type of business you are operating.
For example one of my companies is a service based one. I use Facebook to upload pics of recently completed work. Current clients saw the variety of work we were doing via the page and it resulted in a lot of enquires which resulted in further contracts.
What I have being doing lately however is utilising the Twitter app on facebook and just posting to my Fb page, the app then automatically updates the twitter page.
Also with regards to the paid advertising on fb. The tools and methods they provide you with for targeted placement is very hard to beat.
Like some of the other posters said, it's often about what kind of operation you're running. If you want to develop a deeper relationship, and have more involved conversations, with your (potential) clients - then Facebook is better. So, for example, you've got a business selling solar panels. Facebook is a goldmine for those kinds of "alternative lifestyle" groups - and if you're savvy enough, you can both engage with people by showing them what you've done with solar panels, as well as point them in the direction of your own products. And it can be "official", as in, "Hey, I've set up a solar water heating system. By the way, I sell that same system on my site, if you want to check it out..." OR you can do it unofficially, by setting up a Facebook page for "Solar Water Heaters Inc.", and then posting under your real name, sharing information, and then mentioning that Solar Water Heaters Inc. has a good deal on such-and-such products.
Whereas Twitter... It's social in a different way. I think things can go viral on Twitter much faster than on Facebook, but the 140 characters really limit the depth of your interactions. It works for me in two ways; linking to articles (on news websites, blogs, whatever) and just silly banter with followers. That's nice, too - for example, you won't get big walls of text directed at you if someone disagrees with you, like you can get on Facebook.
Myself? I prefer Facebook. It's better for my business, since there are more seniors on Facebook than on Twitter, and my products are more expensive. Older people are more likely to have the extra cash to spend, hence my focus on Facebook.
Businesses are observed to focusing of twitter more than face book because fb has introduced some features that businessmen do not like more as they were supposed to but twitter still allow them to advertise and share their businesses and updates.
Facebook by far... I tried using Twitter once and they messed up my whole campaign.
With Facebook you can laser target your audience... but it's an art to actually get someone on Facebook to pull out their wallet.
Obviously, facebook is better used for advertising. People find this interesting, especially when they see the ads on social networking sites, and Facebook makes it possible to get profit depending on the needs. Lately, Facebook ads have been a powerful tool for managing business ads, and with other sponsored stories. Right now, it's proven with all its click-through rates, impression that shows leads and assured profits.
I have struggled somewhat with Facebook, and was surprised to find myself preferring to use Twitter.
I work in Product Design, which is quite a specific and niche market in which to advertise online. On Twitter, although I'm limited by 140 characters, it allows me to engage with followers and potential consumers regularly throughout the day without seeming as though I'm bombarding them, and it allows me to stay on top of news/hot topics/whatever's currently trending in the product design field.
With Facebook I sometimes feel as though I'm just spamming people when I try to push our page and services on to them. Am I just going about it the wrong way? I do feel as though Facebook is a fantastic online resource, but one that I haven't yet been able to properly tap into!
Any advice on the matter would be much appreciated, I'm a bit of a novice when it comes to marketing via social media
If you're just talking about promotion, rather than SEO, you should go with Facebook. With over a billion Facebook users, you will always find someone to talk with there about your business. And, Facebook groups are ideal for promoting any opportunity.
As for SEO, you could easily rank your page's 'notes' section. These notes might not have no follow links, but the pages will easily rank. So that means anything you talk about on those pages is likely to be seen by your niche/target audience coming in from Google.
If you choose to go with Twitter, you should be aware of what's trending there, even hourly as 'whats hot' changes quickly.
And, whether or not you choose Twitter or Facebook, remember the key word, 'social', which means friendly. Most people online at social networking sites appreciate a friendly sales approach rather than the hard sale.