The same goes for big companies of course. Intel has a habit of releasing Iot platforms and then killing them. Let's hope the TPU lasts a bit longer.
As for a comparison, it's impossible to say until Google releases benchmark information on the edge TPU, or some kind of datasheet for the SOM.
I definitely have been shocked how fast Intel maker boards have come and gone though. It feels like Intel has written them off before anyone's tried to build a project using one. I have one sitting around here somewhere that's never so much as been powered on.
Intel made some nice little boards, but there wasn't much publicity and actually getting started with them wasn't easy at all because the docs were buried. They were usually modules designed for integration, not standalone devices.
With the Pi you can buy a kit, plug in the SD card and boot ot desktop in minutes.