Several things here.

1) Does extraterrestrial intelligence exist?
2) Do the UFO type craft exist and if so, then are they extraterrestrial in origin?
3) Can we (humans) build craft that will fly almost silently at supersonic speeds in the atmosphere and make abrupt speed and direction changes?
4) Can ideas that are considered strange today, become scientific facts in the future.

My answers are as follows.
1) There is no proof that such life can not exist.
2) There is no evidence that such things do not exist.
3) I believe so.
4) Yes.

You said:

How about something that allows some prediction and/or identification.

If you listen to the signals from the web site that I posted, you will see that the source is identified as the planet Saturn.
Prediction could be made that something similar will be heard again.

You asked:

what do you regard as conclusive?

If we decide to make devices such as these UFO's and we can make them operate properly, then I would say that it is conclusive evidence that they can exist and perhaps they have already been made somewhere else.

You said:

Would you say this is the best evidence you have encountered?

This is only one among many bits of information about such craft.
If it is a fake then it is well done.

Whether all these sightings turn out to be real spaceships or fake imaginations, should not prevent scientists and engineers from applying their knowledge to the task of emulating their operation characteristics.

In the future the wingless craft may become the normal things that we see flying when we look towards the sky.