Pretty simple: need a shoe for tempos/track work so I don't have to waste mileage on my Vaporflys but that's a little more than a regular trainer or lightweight flat. I know the Endorphin Speed used to be the standout in this category but idk if that's the case for the latest version. I saw the Puma Velocity Nitro 2 at a good price on the Better Shoes site before posting but honestly have no reference for shoes that aren't Nike or Saucony in this area. Let's hear your thoughts.