Both of them work really well and my horse lives H24 outside without any coat (except his natural coat.. his hair)
But i don't use them everyday cause he gets quickly dirty again so yeah... The best thing i can say is that dirty horses are happy horses 😊
Double bath the morning of a competition, one wash with regular shampoo, one wash purple shampoo (White n Brite has been my favorite). For the tail, wash it with ketchup (no I'm not kidding), let it sit, rinse, then wash with purple shampoo. Add your condition to make it easy to brush out and it will be bright and shiny! Happy scrubbing!
I struggle with this as well, what I try to do as much as possible it to keep him clipped, and when I use shampoo I'll either use some kind of horse purple shampoo or the betadine method. The purple shampoo shouldn't be used every day though!
I also find that having shavings as a bed instead of hay helps a lot.