Yes, this is the dilemma. Most of us change plans, goals, management techniques and who knows what else as we go along. This has to be your decision, none of us can make it for you.
My general suggestion is to keep as few boys as you can and still meet your goals. Then find a way to do it. That may involve isolations, bachelor pads, or getting rid of chickens.
The way I read this you know you want to get rid of one and know which one that is. The other you are still undecided on. My suggestion is to remove that one immediately. Isolate him and get rid of him as soon as you can. Don't give hm time to become even more attached. You know what you want to do so just do it. Getting started can be the hardest part of this.
Observe the other cockerel with your four pullets. See how they get along. Make your decisions based on what you see, not what some stranger over the internet tells you that you will see.
If you are sure you eventually don't want any boys, I'd get rid of them both now. I think it will be easier to only go through this once.
Good luck! It can be a rough decision.
