I regularly test among Fujinon, Tamron, Theia, Pentax, and Computar. Overall, Fujinon has been the best overall for producing image quality in 1-3MP cameras in well lit and low light scenes. Their non Day/Night lenses still perform very well in low light and there is minimal focal shift when using a day/night camera.
Tamron lenses always test ok, but like Computar, I see more trouble with depth of field in these lenses to keep an entire scene in focus. Image quality is good out of these two brands, but Fujinon lenses are competitive on price and have given me better results.
Theia lenses have been the best overall from my testing but they have a gap in their offering with a 1.8-3mm option but then jump to 9-40mm. But they are rated for up to 5MP resolution so you have a lot of flexibility in cameras to use them with and they do offer the ultra wide options without lens distortion. Depth of field is also very good with Theia. If we could get customers to pay the price every time, we would probably use Theia in every project if the mm range works.
As John pointed out, the Pentax lens is the easiest lens to deploy because of the unique focus mechanism. It's just limited to 1.3MP resolution and from my testing still has some trouble using cameras with auto backfocus. They have a similar focus option in a 8-40mm that is rated up to 3MP but it is a massive lens and has a constant f-stop so you will get some depth of field issues.
Kowa still produces great lenses, but their MP lenses are 2-3x in price from everyone else which may be why you don't hear about a lot of people using them.
I hope that helps.