Well that depends but the usual answer for most small business is cable. DSL just isn't fast enough for multiple users and the price difference is typically negligible. FiOS is new, not available everywhere and where it is it is mostly and adds extra layers of potential problem (something I hate so much I have a whole category dedicated to the idea). In other words FiOS isn't ready for prime time in the business since. When they work out the bugs and get universal availibilty it will be great but I have seen too many problems.
Cable is typically a quick install that requires basic hardware from the provider (a cable modem) and usually comes with a static IP address on a business line. Cable for business is usually no different than residential cable internet except that it costs more (and maybe comes with a static IP) which stinks but is understandably common practice anything for the "home" costs less than the "business" version even though feature wise there is no value added components. But the bottom line is the cable provider is the best way to go in an office from three to 15 employees who regularly use the computer, after that talk to the telecoms about a "partial T" and be preparred to dish out the money, your bill just quadrupaled .
What cable can't necessarily offer you is a PBX phone line. (A multi-line phone system - usually four - or five with a dedicated fax) which is another way businesses get bumped up to major telecom providers. Again this is one of those moments where you have to look at the costs objectively. VoIP (voice over Internet Protocol) is starting to come into its own and while there are a lot of players in this market, there are an awful lot of factors that play into the effectiveness of implementing a VoIP office. VoIP is a phone system that uses your internet data connection to travel over the internet which offers some distinct advatages to those that can understand the process. One factor is how good your internet connection is. Ignorance is not bliss here. I saw a case where a customer paid for DSL ( a slower connection) to the phone company and then paid another VoIP company for addtional lines. Forgetting to put the DSL (he had no idea) filter a phone jack and he had no internet and no phone. The problem with options is not understanding what you are really choosing. Some business these days still use good old fashioned phone land lines and that works JUST FINE, but if your business spends an awful lot on long distance, well you may want to reconsider.
If this all confuses you. Good. The whole point is know what you are buying and if you don't, don't buy it. If you are stuck in a DSL contract, stick with it if is working for you until your contract runs out and don't let your employees stream internet radio. If you are opening your doors day one, go cable unless you are starting out with fifteen or more employees who regularly use the computer then consider more. Don't think just because they are not on the internet 24-7 this shouldn't matter because there is more to the internet than web surfing. Downloading software and operating system updates, email, research and other very legitimate work activities rquire the internet and bandwidth without anybody goofing off on twitter.