Hi CodeTrainer,
Here are the differences between SETI and biological ID, as I see them:
1. Mathematical models of what kinds of signal are NOT intelligently designed
SETI has mathematical means of falsifying the claim that a signal is of intelligent origin. For example, they have models of what kind of signal would result from a pulsar, what kind of signal would result from background "noise", etc. They can use these models to falsify claims that a signal is intelligently designed.
ID, on the other hand, has no clear model of what biological "noise" looks like, so ID researchers are unable to falsify a claim that a signal is intelligent.
2. Mathematical models of what kind of signal IS intelligently designed
SETI researchers make clear statements about what kind of signal would be considered intelligent - i.e. narrow bandwith signals that can't be produced by known natural processes in the cosmos.
ID researchers, on the other hand, do not have a model of what intelligent design in the biological world would look like.
3. An empirical research program based on falsification
SETI researchers are engaged in gathering empirical data from the world, and falsifying the hypothesis that such data contains intelligent signals. While SETI researchers have never found an "intelligent signal", this does not meant that they have achieved nothing in scientific terms. In fact, they have falsified the "intelligence hypothesis" thousands upon thousands of times. If you install the SETI@HOME screensaver, what you are doing is falsifying a specific well-formulated hypothesis over and over again.
ID researchers, on the other hand, are not engaged in gathering empirical data from the world which can be used to falsify the hypothesis of intelligent agency.
4. Reliable research methods
SETI researchers have tested whether their experimental setup is capable of identifying intelligent signals by getting a satellite to broadcast weak signals toward earth. They were able to identify such signals reliably. They are also able to identify TV signals, etc. So they are confident that their setup would also be able to identify similar signals of non-human origin.
ID researchers, on the other hand, have not tested the reliability of their research design.
Hope this helps,
Mick