Cloud-based antivirus can provide better malware detection than regular antivirus. Many antivirus vendors develop different signatures for a given set of malware. However, signatures will differ from one antivirus vendor to another, and some of the antivirus obfuscation techniques that can be employed may not dodge all antivirus products successfully.
However, there is a drawback to this approach. If you wish to implement a cloud-based system, you will need a site license for every product you are planning on implementing. Such an approach can get costly. Personally, I do not believe this to be a viable solution because it is trivial for an attacker to create a virus that can bypass many if not all antivirus products buy testing it at sites line Virus Total, a free website service that scans files for obvious viruses, worms, Trojans and other malware.
I would also recommend looking into other products that take an application whitelist approach to malware defence. With whitelisting, an organisation's systems are only allowed to run software that is approved by the IT department. Anything new (including many types malware) is denied by default. Products from Lumension Security and CoreTrace, as well as Cisco's Security Agent, show promise in this area.