You are a Manager, you have 10s of people working with you on multiple projects. All 5 fingers of a hand are not equal, you must understand the fact of nature. Use thumb for the purpose it is developed for, and other fingers in same according fashion to use differently. Don't compare John with Paul for their work culture, reputation and/or results, both are as good as same but it can be in different areas. You are also equally responsible to identify their expert areas as they are into themselves, so you can take best use of all your subordinates. Don't blame on them, if you can't use them efficiently.
We are 2 brothers, born and brought up by same parents but we both are into entirely different fields and both are outside of family business line. Why it is so? We both are doing good in our areas. Same is the case with my 100s of friends, old classmates, colleagues and other people with whom I travel in public transports.
I can't, or won't suggest how to identify people skills working with you? It's your job because you are promoted to the suitable and responsible position for doing that only.
During my masters back in year 2000, I studied a few books on various management subjects, and the bottom line for all was, "MANAGE-MEN-Tactfully". In practice, I'm finding the phenomena changes to "Manage-Men-Timely" (only on times when problem comes). Famous author and PMP trainer, Oliver Lehmann has well said, "Clever project managers pass problems to others; smart project managers build a reputation as problem solvers.".
Come on... Let's be practical on this, and call duck a duck, eagle an eagle, and horse a horse. It's not possible for horse to swim, but none of duck or eagle can run as fast and long as horse.