Over the last 15 years or so I have dealt with at least half a dozen of the quick-turn prototype fabricators, for both hobby and commercial projects. All of these were fairly straightforward, two-sided boards. Although there were variations in “quality” (tolerances, precision, consistency, attention to details, etc) I never received any boards that were truly defective or unusable due to fabrication problems. (Layout errors are another story.)
Vendor selection was driven by price and delivery schedule. I believe it pays to shop around, but it was often difficult to perform an accurate comparison of one vendor over another. Pricing algorithms vary widely - a board which crosses the line into a higher-priced size category at one vendor may still qualify for a lower price at another. Be careful if hole sizes are truly critical (that’s seldom the case), since there are several methods of mapping the sizes on your drawing to the vendor’s standard drill sizes. Some features (e.g. solder mask colors, conductor plating materials, narrow trace/space dimensions, etc) are “standard” with one vendor but “extra cost” with another. Many vendors run gimmicky promotions that a particular job may, or may not, qualify for. (Delivery time in particular can be difficult to compare, especially when a quick delivery is used as a promotional feature. Submission cut-off times seem to always conspire with international time zones to add an additional day or two to delivery schedules. Some vendors count the day of order submission as “day 1” while others wait until the following day, and occasionally a vendor doesn’t start the clock until the order has been reviewed and approved by his internal production department.)
For larger orders - more than, say, 50 boards at a time - I was always at the mercy of company purchasing departments that worked from lists of approved vendors, and I seldom knew who the actual vendor was.
The original posting isn’t entirely out of line. A particular vendor’s ability to exploit some feature of KiCAD, or incompatibility with some other feature, is information worth presenting here. I recall a recent discussion where it was determined that a certain vendor didn’t support true circles as graphic objects, and circular shapes had to be created in KiCAD as an array of arcs.
Dale