I think you are intuiting your way into realizing that people should, in general, NOT be compared against each other but each appreciated for their uniqueness.

I think you should also stop being so hard on yourself for being the cause of it all, but instead relax a bit and just see it for what it is - a typical and rather banal love triangle with you as the main vertex. There is no crisis, nobody is dying, in pain, without shelter or food, so the situation is not THAT serious and your reaction to it is overstated. It is important not to overreact and retain some sense of humor. And clearly hating yourself is unproductive.

Since they know what is going on so it is not like you are deceiving somebody, I would just take your time to figure things out without giving yourself a deadline. They are able-bodied adult men; they are not little children or frail elderly. Able-bodied adult men should be expected to be capable of tolerating a little uncertainty for a little while. Or maybe you can go back to living with the original guy but also have a relationship with the guy from work from some to time? Does it really have to be an all or nothing approach? Maybe listen to your gut feeling that tells you that people should NOT be compared with one another? At least at times?

But at any rate, whichever way you decide, recognize the situation for what it is and do not overreact because no catastrophe has happened and there is no terrorist threat hanging over your head.