Pure all the way from instinct, but without an ingredient list can't be 100% sure. Have you searched both brands in posts on here? Very different philosophies and ingredients in most cases.
I cannot comment on Pure, but it looks like good stuff.
I do feed TopSpec to mine and whilst the Comprehensive Balancer is great, it does pile condition on them so unless your horse needs a high calorie diet, I'd use their Lite or Cool Balancers.
ETA - just for reference, I used to the Comprehensive Balancer to get a poor doer into show condition and it worked. I now use the Cool Balancer for a Thoroughbred who is a reasonable doer but definitely does not need such a rich formula feed (it would probably worsen his already prickly persona).
I have wondered about the Pure balancer, my reservation has been that the feed seems to have lot of different types of what appears to essentially be chaff. Haven't looked into Topspec as they don't appear to have the best name, but this is a personal observation so it could be misplaced.