It depends on your business!
Traditionally, domain names identified a country or physical location of a website.
For example, .co.uk is pretty obviously a company in the UK.
However, .com was associated to the US, but in recent years, it has become much more globalised
A new breed of gTLDs (Generic Top Level Domains) will be on sale from 2014 / 2015 - with the suffix specific to a descriptive topic, or geographical place - so that businesses can better align themselves or their brands to a specific area or description. For example, the .london domain will soon be on sale, as will others such as .music, .cafe, .app and so on.... read more here on the official ICANN site
The best approach is perhaps to try to secure a range of domains. For example, you may wish to grab a variety of domain extensions to assist your customers in finding you, e.g. .com, .org, .info, .net and so on.
If you need assistance deciding, just let us know.