You should buy the best helmet you either can afford or are prepared to pay for.
I wouldn’t want to be regretting anything regarding my helmet while I’m doing an over the bars pirouette.
On my over the bars pirouette manoeuvres, I can recall thinking,
Body armour, check
Elbow pads, check
Knee pads, check
Helmet, check
Gloves, check
It’ll be fine.
I certainly wouldn’t want to be thinking
helmet, wish I’d bought the better one, cross