Go to a equipment outlook that carries boxing gear and try them on. Theres lots of brand names and picking gloves should be personal. As for spar gloves I used and offered in my gym 14oz. gloves (Everlast, Shevland, Reyes) 16oz are to big compared to fight gloves (10oz)(8oz).
However if everyone wears 16oz in the gym you spar at then by all means buy 16oz. Ray.