Data projector needs to be powerful enough to produce very bright image without blacking out auditorium. That means the brightest possible projector for best results. Consider how dependent you are on the data projector bulb, not just for this presentation. Remember that these presentations are on the future and it looks terrible to have a techno-failure. That's why most conferences now line up a second projector as backup, even if the second one has a far lower technical spec.
Most projectors are bulky and noisy.
Therefore the worst location is on a desk in front of a small to medium audience. It is preferable in such cases to house the projector out of site underneath the presenter's table, angled slighty up towards the screen. The image distortion is usually worth the reduction in noise and untidiness. Spotlights Attention to stage lighting is very important, so that the speaker can move and engage audience interactively when appropriate without disappearing into semi-darkness. A key test is how dark the screen is when the projector is off.