Wirelessly posted (Opera/9.80 (BREW; Opera Mini/6.0.3/27.2354; U; en) Presto/2.8.119 320X240 LG VN530)
Scanners have AM/FM/FMN/P25 (and X2/Phase II if you have the right models), and can trunktrack, also with the right models. They have a single receiver and antenna input, versus typically dual receivers and multiple antenna inputs in communications receivers. They have much faster scan rates, and have a much greater memory capacity than communications receivers. They're typically less expensive than communications receivers due to the use of less expensive circuit components, with correspondingly lower specifications when it comes to sensitivity, selectivity, etc.
Communications receivers have a much wider frequency coverage, with the widest typically covering from about 100 kHz continously up to 2 or 3 GHz (and goverment/industry sales include the cellular phone ranges), have AM/SSB/CW/FM, but only a few (1 or 2 from AOR?) models have P25 capability, with an optional board. You can usually select various bandwidths to go with your mode selection. None have trunktracking to my knowledge. More expensive components mean better sensitivity, selectivity, etc, than your typical scanner.
If you like to sit on a specific frequency looking for weak signals and/or DX, a communications receiver is probably a better choice than a scanner. If you enjoy listening to your local public safety agencies over multiple frequencies, then a scanner is a better choice.
I would have loved an Icom IC-9000