Taxi services serve people. Research the internet thoroughly so that you get to know what users are talking about various airport transport means. Check what users have to tell about the punctuality of the cabs, professionalism of the drivers, safety features of the vehicle, courteousness of the company, approach towards clients, and the like.
You have to choose a car company that has satisfied all its customers and one that enjoys immense goodwill among its users. You can also guess taxi cost online.
Check for various sites to see the user reviews so that you get a fair idea about a particular car operator. Never take decisions based on reviews on one site alone, as these could be biased.
Yes, this should be the last point that you should consider when choosing airport transport cars. While the cost factor is important, it is not more important than your safety, isn't it? Never fall prey to the low prices or promotional offers/free rides offered by these services that don't enjoy a great reputation in the market.
By doing this, you are putting your safety at great risk, for which you need to pay a huge price. Therefore, choose taxi services that charge you reasonably and take care of your safety in the best way possible.
Never believe all the advertisements in which these services make tall claims about their low prices. You must rather believe the facts and figures that emerge out of your research before you make this decision.