As someone who has logged hundreds of nights in Choice properties due to spending far too much time in smallish towns throughout the country, here is my take:

Sleep Inn: Generally new construction and fairly comfortable. The showers are always big and the wireless internet nearly always works. While nothing special, Sleeps are generally the most consistent of the bunch.

Clarion: This is a full-service property that was a Marriott in 1975 and then became a Holiday Inn in 1992 and then became a Clarion in 2004 (Bakersfield, CA for instance). It was probably nice once, but no maintenance has been done in 25 years. There are exceptions to this, such as the Clarion-PDX. Also, you will occasionally find a converted apartment-type building, such as the one in YUL.

Comfort Inn: Hit or miss. Could be new construction and fairly decent (Sonora, TX for instance) or could be a complete dump. Wireless may or may not work.

Comfort Suites: Like the inn of the same name, but the rooms are bigger and the hotels are generally newer. These are not really suites, btw, just larger rooms with a divider. Generally a pretty safe bet when available. The one in AUS is decent.

Quality Inn: Remember what I said about Clarions? Take that Clarion and add 10 years of no maintenance. There are a few exceptions, but by and large, Quality is generally a very small step above a Rodeway. If you want to see the shining example of this, try the Quality in San Angelo, TX and get a room on the back side (Bug infested and worn out... I had to change rooms 4 times...).

Cambria Suites: Haven't tried it yet, but may check out the one in BOI next month for giggles.