I used both. Windows 3.x was a horrible technical kludge, but it was cheaper and came with more software included. OS/2 felt very much ‘IBM’, well designed but when you started it up there was notepad and that was about it until you installed more software of your own; AFAIR you didn’t even get Solitaire. If I remember correctly, it also required a 32-bit CPU and twice as much RAM as Windows?
By the time IBM realised that Microsoft were winning they were really too far behind to catch up. Particularly after the ‘OS/2 NT’ project mutated into Windows NT.
Most of the urban legends that ‘a better product didn’t sell as well’ turn out to be because the ‘better product’ wasn’t better from the purchaser’s viewpoint.