I would recommend the Nike Zoom Elite. This shoe is light enough for tempos, workouts, and track work, plus durable enough for long runs. If you're a midfoot/forefoot runner the Kinvara will not be durable enough. The Boston Boost can be a bit too soft for racing/workouts, don't get a true enough response from the shoe (love the Energy Boost for training - but for a faster shoe the response isn't there with the Boston) The forefoot Air unit in the Nike is a nice savior for long runs. Another consideration could be the NB 890 (the Vazee Pace just replaced it, too early to give a recommendation for that though)