cowboy magic all the way! i have used all of the above mentioned and:
1. MTG is wonderful for mane growth--never used it as a detangler as it is so greasy and makes my horses mane get full of dust and debris
2. Showsheen--i have used at shows at a body shine of sorts, and it does keep the mane slick but it does that last.
Cowboy magic os by for my favorite, a little pricey but let me tell you it works, i apply it once every 10 days and it is always easy to brush through even in between applications.
~A truly Fancy Pirate-Pirate-By All Time Fancy-Bay overo yearling.
~Mia-6 year old Thoroughbred mare. Ex polo Pony