The battle format decides what the rules of the battle are, e.g. what Pokemon are allowed, singles or doubles, etc. Certain Pokemon being allowed could make one Urshifu form better than the other. There is also a popular format (SWSH OU) where Single Strike Urshifu is banned.
Knowing the format you're playing will allow us to give a specific and definitive answer. If the videos you've watched haven't discussed individual battle formats in competitive play, then that's why you haven't gotten a straight answer. You can't give a straight answer for competitive play in general.