I was in a barn that used pea gravel in its runs. Hate the stuff.
Pea gravel remains unstable, like ball-bearings forever precisely because of is pea-round shape. If you put it over geotextile, the horses’ hooves will poke through to that in short order. The pea spot will smell. It is hard on horses who have any frailty or problems getting up and down. It will create bedsores for those horses who have any arthritis at all.
I think it was a farrier’s nightmare where we were-- in Oregon’s wet, western Clay World. When you mix pea gravel with clay, it becomes a very rough, compacting mix. You need to pick hooves religiously or have horses with any tendency toward sore feet/soles to get hurt by the mix.