I don’t feed either of the feeds that you mentioned, though I have fed Triple Crown in the past (so you might want to skip over my post if those are your only two options).
But, just in case anyone is interested in other feeds,
about two years ago I started feeding Junior Glo (by ADM) along with their Gro-strong minerals supplement to my broodmares and foals as well as my young horses. I noticed a huge difference in both how well the mares kept weight on and how healthy they looked (shiny coats, even in winter, great feet, etc.), how good the foals looked when they were born, and how well the young horses kept their weight and looked fit and healthy. I have tried all of the other top brands, and this is more expensive, but well worth the cost to me.
Others have commented on the difference in my foals and other horses as well, which is what really sold me on it.
It has 19% protein, 6% fat, and 20% fiber. The other thing I really like about it is that it contains flaxseed, soybean meal, probiotics, and other beneficial “stuff,” and has less starch than some other products. This is their product description:
JUNIORGLO is a premium feed for foals and growing horses with protein, energy, vitamins, and minerals balanced specifically for safe, rapid growth. JUNIORGLO is especially effective in programs for show and sale preparation of weanlings and yearlings. JUNIORGLO contains Stabilized Rice Bran, Omega Flax ground flax seed, and Soy Shine along with highly digestible fibers from alfalfa and soybean hulls and is low in starch and sugar. It does not contain whole corn or corn starch. JUNIORGLO is also excellent in broodmare rations, especially when only low protein forages are available.
and a link to the product, for anyone who might be interested:
http://www.admani.com/horse/Products/Horse%20JuniorGlo%20Feed.htm
I don’t sell it by the way. Just as a strong believer in its worth. 