Serviced offices differ vastly from just rental offices, so you'll need to know what it is you want before you purchase or rent office space. Serviced offices have a plethora of services associated with them, such as dedicated reception teams, air conditioning, Wif-Fi networks, free refreshment areas, AV equipment and networks, together with other essential office services.
Renting an office space however, can just give you a space, in which you need to place your desks, network and other facilities. So, how long do you want to be at the office space? Do you want to stay for a long time, in which case, can you sign a long term rental agreement? What happens if the landlord wants you out? Do you have protection built in for the investment you make in fitting out that office? And then there are the costs of refurbishing an office. If you rent it, can you afford that in the short term? Are you a start up company? Might a serviced office space be more to your requirements, with it's lack of need for long term agreements and the fact that facilities are there immediately for your use, including Internet?
Only you can ultimately decide what is best for your office requirements, be it serviced offices or office rental or purchase...