I'd love to chat running hydration vests with you! I'd definitely suggest trying a few on, it's almost as personal to fit as your running shoes. But...some of my favorites from personal experience are the Salomon S-Lab vests, Ultimate Direction Ultra Vesta or the Nathan Vapor Howe. Other factors to consider are do you prefer a back bladder or soft flasks in the front pockets? Personally, I lean towards soft flasks in front...easier to refill at aid stations and less sloshing around. Hope that at least helps to get you started!