A friend and I researched this extensively five years ago. My flatware started spotting after a kitchen renovation in which we installed a dishwasher with a stainless interior. That's one issue.
The second issue is that there are indeed different qualities of 18/8 and 18/10 stainless. If it's coming from China or India or Vietnam it can still have the chromium & nickel content to qualify it for 18/10 but still be a poorer quality steel than what's manufactured in the US or Italy. There is a process called passivation that is applied after manufacture, and that speaks to the quality of the flatware as well.
Here is a good thread on the stainless/spotting issue:
Oops! Sorry, page not found. Error 404 From the first page:
"for the main problem you can be sure that the quality of steel is the source. If you can find flatware (and other products) with steel manufactured in the above countries (US, Japan, Europe) you will have much better quality, and products that truly DO stain less. Remember that the stainless steel is still 70-80% iron, so it will still rust if the quality is poor or it is stressed by chemicals that are not good for stainless steel. If the steel is full of inclusions caused by poor manufacture and use of high amounts of scrap iron you will have rusting even in normal uses."
I have very good quality stainless from Italy. It started spotting in the stainless interior dishwasher. Apparently that just sets up a corrosive environment. I hand-washed the stainless after that, until we came here. Now with my plastic interior dishwasher and the use of Finish Powerball, I don't have a problem. We do have a whole house water filter and water softener.