If you must turnout in boots then go for something breathable (i.e. not neoprene!) - teh equilibrium hardy chaps are good & ok to leave on for 12hours
Not a lover of them since they tend to generate more problems than they solve.
With my horse ive opted for individual turnout and a general awareness of the ground conditions. He occasionally has turnout boots on if im predicting fireworks from him... but only because he has a very active hindleg and tends to cut into himself.
If you insist on using them, the equilibria ones are quite good... although ive still seen some nasty rubs from them also.
ETS they're quite expensive but in my experience the cheaper ones move and rub like mad and in that case, its much better for your horse to leave them off :|