How to choose good quality Chinese slicer knives?
Short answer:
 I've only heard good things about the CCK #1 small slicer, and would suggest that.  If you're new to the style of knife, pick up a cheap carbon-steel Dexter Russell one for like $20-25 at your local Chinatown.

Long answer: Chinese slicer knives (more commonly called Chinese cleavers) are multipurpose knives, so they fill the same niche as French-style chef knives.  They're common options for cheap restaurant knives, and I've seen them used professionally.  I now use a Dexter Chinese Cleaver as my primary knife at home.  

The common features of Chinese cleavers are a squared-off, deep, often carbon steel blade, bamboo barrel-style handle, and pure awesomeness.  Generally the blades are around 200mm long x 75-90mm deep, or about 8" x 3".  As you note, the blades are not as heavy or thick as German-style cleavers, so they can't handle bone.

Although they get mentioned a lot for vegetable chopping, Chinese cleavers are remarkably flexible for both meat and vegetables. You can find videos of Chef Martin Yan deboning a chicken in under 30 seconds with a Chinese cleaver. The deep blade makes chopping thick objects simple, where the squared corner is remarkable for fine detail work.  The spine of the knife can be used to tenderize meat or scrape cutting boards. The broad blade is perfect for transferring cut product to a pan.  You can even use the handle for crushing spices!

The carbon steel blades can be love or hate for many people.  Personally, I love how mine takes and holds an edge comparable to the most expensive stainless steels.  The fly in the ointment is that they can rust right before your eyes if you cut lemons or acidic tomatoes.  They should always be cleaned and dried PROMPTLY after use, to avoid rust. Between use, I oil mine lightly with vegetable oil, as an extra precaution. Between this and the water-intolerance of the bamboo handle, they do need some special care.

Although stainless-steel cleavers are becoming more common, I really think it defeats the point if you use one.  They're supposed to be cheap and ugly, but workhorses. A good Chinese cleaver shouldn't set you back more than $50 in your local Chinatown or online... mine was about $25 and it does dang fine, though I will probably upgrade to a CCK #1 eventually.