It really doesn't matter. With a hard drive, I always recommend the /r switch because it implies or includes all the functions of /f, plus it will attempt to locate and recover/repair a bad sector, if possible.
On a SSD, any function that cannot be done will simply be ignored. So running with the /r switch is not detrimental. Whether it does any good is another issue. My point is, however, if you ran with /r, it does no good to run again with /f.
As for time, it is the /f switch which is consuming time. And it can take a very long time to run on a large drive. It typically is best not to interrupt checking and just let it run. While it can take many hours and appear to be hung, it will eventually finish.
Since you tried this SSD in two different computers and were unable to access it from both, it would appear the drive itself is faulty. Did it ever work properly? You could try formatting it but frankly, and especially if still under warranty, you might be best served by contacting Samsung.