So you need an adapter that can output from your MacBook Pro or Air to a projector which uses a VGA interface? I think if you’re after quality and reliability then stick with Apple. It’ll cost more compared to other options but that’s what you pay for – peace of mind. The Apple Mini DisplayPort to VGA Adapter MB572Z/B is a great option selling around $29.
That’s not to say that the other cheaper brands dont work. They do – and will probably work for a great deal of time. If your on a tight budget there is the VicTsing Gold Plated Thunderbolt Mini DisplayPort to VGA Male to Female Adapter which would cost a fraction of the price of the Apple counterpart yet carries good reviews! This will only set you back $12. There are many other but these are probably my top 2 choices for now.