Ultimately, the answer about this UX style is very much the same as a question about writing style—there's no objectively right answer, but you have to be consistent.
For example, you can pick up any number of style books from Strunk & White to the Chicago Manual of Style and get different "right" answers about writing style, but any editor will tell you the ultimate solution is to be internally consistent.
The arguments for each approach have merit. "OK on the left" designers will argue that because we read from left to right, the positive response should be first. "OK on the right" designers will say that the positive response carries the user forward, and because we read from left to right, forward progress should be on the right.
My personal feeling is that there's another argument for OK on the right, which is that the majority of users are right-handed, so the default choice will be closer to their dominant hand if it's placed on the right.
Then again, I may be looking for evidence to support my preference, which probably arose from the fact that I began designing on the Mac, so I was conditioned to Apple's "OK on the right" standard at an early age, and I've simply conflated "familiar" with "correct."
So the answer from this veteran UX designer would be: Use whichever placement your users are going to be the most familiar with, but whichever you choose, be 100% consistent with the choice you make.