In the past I have usually gone with performance trainers for all of my workouts and flats for races, but my most recent pair of trainers is heavier than what I am used to. They are great for easy days, but my legs feel heavier on repeat and tempo days. In this case is it more beneficial to get a new performance trainer for repeats and tempos that are more suited to faster turnover or to use the heavier trainers for both and push through the repeats and tempos in heavier shoes to gain strength and so that the weight differential is more noticeable when I put on my flats to make them feel like little more than socks?