Brightness and color display
Probably the most important thing about projectors is the quality of the image projected. But what makes a good, clear and crisp image? Of course brightness is an important factor. Believe in your natural eyesight are important if you are evaluating the projector output content, especially projection during daylight conditions. In a dark room you could have a good and bright projection for most of the projector. But brightness is not the only determinant factor. Maybe even more important is the colour display. In some cases increasing brightness leads to a reduced colour space which makes colours pale and unnatural looking. Good Projectors are using color wheels with good color filter in order to see colours as they are meant to be in your video or picture.
Resolution and contrast
Another factor is the resolution. The higher resolution the more detailed the presentation of the image will be since the image is composed by more pixels and for that reason it seems sharper. The contrast also is an important measure indicating the difference between the brightest white light and the darkest black light. The higher the contrast the better and brighter the projection will be perceived. So it is important to have all these factors in mind but it is not always true, please beleive in our human eyesight and not what is on specification. Till today, there are no cyberpolice that can stop anyone from posting untrue technical information in the form of marketing