h5 or h6


weak kingside alert
go on...
a4 b4 c4 d4 e4 f4 g4 h4 iis the best opening

They’re both completely fine but one point to note is after 4…h6 5.g4 you have to retreat the B to d7, as after the natural 5…Bh7 white has the disruptive 6.e6 which is somewhat of a problem.
so you could say that …h5 allows you to keep the B on its active diagonal at the cost of being a bit more structurally committal.