The smallest transceiver I have is a Yaesu VX-1R. I've had it since new. Still haven't found anything smaller.
http://en.wikipedia.org/wiki/Yaesu_VX-1R
It's a great 'scanner' too, but won't do trunking of course.
As for the MOTOROLAs, Tony 'talivar' hit it right on. The big radios hold up to the abuse of daily carry and have a long lasting battery. I love my big Johnson....heheheh
http://www.eham.net/reviews/detail/6736
http://www.efjohnson.com/
As for scanners and their sizes, I have a PRO96 and BCD396T. To me, the '96 has better receive qualites and audio. Yet I find that I carry my 396 with me all the time due to it's smaller size. The '96 stays in my vehicle or in the house.