Of the four non-widescreen projectors with zoom lenses, you can see that the Panasonic can be placed the closest to a given sized screen. For many presenters, this is a real plus, as it's often easier to place a projector near the front of the room than, say half way back.
*The Epson offers a digital zoom instead of optical. It actually has more range than any of these other projectors, when using the digital zoom, but it does degrade the image slightly - see the S4 review for more info.
Inputs and Outputs
Since this is explored more in depth in the individual reviews, the goal here is to give you a sense of the differing flexibility of these projectors. The individual reviews each have a photo showing the input panel of their respective projectors.
All (rather surprisingly) have a monitor out for feeding the signal to a separate monitor. This isn't needed for laptop use, but needed if you want the signal also on the monitor of the computer you are working from. In the case of the Panasonic, you can turn off the monitor out, if not needed, toggling it into becoming a second computer input.
Two of the projectors, the Optoma TX-700, and the Mitsubishi HD4000 have a digital input - the Optoma, a DVI-I, and the Mitsubishi, an HDMI. The Optoma's DVI-I can accept digital, or a traditional analog signal. Though few need a digital input for business or education, it is desireable for many specialty uses.
Including those two projectors, three in all can suport two computers, the third being the Panasonic LB60NTU, if you are not using the monitor out. In fairness, however, the Panasonic can actually have 18 projectors hooked up at the same time - with 16 of them wireless. That sounds like overkill, but having several wireless computers hooked up at once has a lot of appeal for many company meetings. This makes the Panasonic the king of computer inputs.
Component video input, the highest quality non-digital video, is accepted by all six, but in all cases but the Mitsubishi, it gets fed through the analog computer port. So if you really needed to input component video, the Epson, Dell, and InFocus could not also have a computer hooked up at the same time. Of course, though, all have S-video and composite video, so that's only an issue where you need that extra jump in image quality.
When it comes to audio, not one of these small projectors can fill a room with quality sound, but are sufficient for voice and lower fidelity music in rooms with, say 20 people or less. Three of these projectors, though can control external powered speakers with their audio outputs, the Panasonic, Dell 2400MP and the InFocus IN26. Only the Panasonic LB60U and LB60NTU, though, has more than one audio input (they have 3), so if you wanted audio from a video source and from a computer source both hooked up, with the other projectors it requires some jerryrigging and compromise. I better note that the Mitsubishi HD4000 is the only one of these four without a speaker.
All six projectors have some degree of "command and control", typically through a USB port, which will allow operation directly from a computer, or also, in the case of the NTU (wireless) version of the Panasonic, from a wireless network.
In summary, if you need more than one computer input, or have specific high quality video needs this would be an area that would easily allow you to narrow the field, with the Panasonic and Optoma TX-700 the most flexibility, along with the audio free Mitsubishi. The other three are pretty standard - one computer input, one out, and have an issue if you need component video and computer. Overall, the LB60 projectors and the Optoma are the most flexible of the six, followed by the Mitsubishi (if you can live without audio).
Time to consider the Image Quality of these six portable projectors.