Adizero Prime X 2 vs Endorphin Pro 4

With 50mm under the heel, the Adizero Prime X 2 sits a full 10mm over the World Athletics limit for road racing, so no record or championship result run in it will stand. adidas built it that way on purpose, as a carbon-plated experiment in how far stack can go, and most reviewers ended up treating it as a very expensive super trainer rather than a racer. The softness won nearly all of them over. The weight was a different story: it put on a lot over the first Prime X, and several testers struggled to hold faster paces in it. Lab testing and two of the reviews rate it well for long runs and marathon-pace sessions, while one US panel called it a step backwards and preferred version 1. Coach's UK review lands in the middle, calling it great fun but priced above legal racers that do the job better. If you want an adidas marathon shoe for race day, the Adios Pro 5 is lighter, cheaper and legal. We'd buy the Prime X 2 for how it feels on long miles, and only once the price has dropped.

Saucony softened the Endorphin Pro for version 4, and most reviewers think it was the right call. The Pro 3 was quick but harsh by the second half of a marathon; this one gives up a little of that snap for a ride that stays comfortable over the full distance. Women's Running UK rated it highly and recommends it for marathon and half marathon runners who care more about finishing strong than about the last few seconds. The trade-off is weight, since two reviews found it heavier than the Pro 3. It's a carbon racing shoe with an 8mm drop and a stable, wide base, which makes it one of the easier super shoes to run a whole marathon in if you land on your heels. The Endorphin Pro 5 has since replaced it at a lower RRP, so the Pro 4 makes most sense when a retailer is clearing it well below £230.