Anyone who tells you a single company is the best is full of it. Different places do well with certain traffic and worse with others. If your websites are ones you just bought and get 0 traffic, stop thinking about parking. Parking is for people with traffic (mostly type in) and isn't some magical revenue maker for unprofitable domains. If your domains don't get any, move beyond parking, go develop adsense minisites or blogs. Parking is a waste of your time unless you've got traffic. That said, if you do have traffic consider where its coming from, US traffic/European traffic is highly valuable compared to most of the rest of the world. Some companies do better/worse for for foreign traffic, then targeting.