Lucky you getting less than 50% males.
Which one to keep depends to a certain extent on your goals.....
Are you intending to breed or just keep him as eye candy or flock protection (few roosters will take on a predator but they will usually call an alarm)
If breeding, what are your goals... pure breeds, mixed breeds, good egg production, bonny coloured eggs, dual purpose so there is some meat on the excess cockerels, multi-coloured flock.
Eye candy is straightforward..... choose the handsomest in your eyes
Flock protection, keep the one that is most alert.
Overriding factor on all of the above is that the one you keep should display a good temperament with humans and the pullets, however bear in mind that if you remove the others that temperament might change, so worth isolating all of them from the hens and then trying each one in with the hens on his own for a week or two and see how that goes. That should give you an indication of his true nature. Spend time watching how he interacts with the hens, they have to live with him full time and injured harassed hens don't lay well, so important to choose one that is easy on them.
Good luck making that decision. I know it's not always an easy one.
Regards
Barbara