Hood or crew neck
That is the only real decision, and it depends on what you want from it. A crew neck slides under a jacket without bulking up the collar, works at the office, and leaves the artwork fully visible. A hood keeps the wind and light rain off on the way out of the gym and holds heat longer, but adds volume at the shoulders and covers part of the print when it sits down.
Plenty of people end up with both, one in the gym bag and one in the wardrobe. If you are only buying one, start from the season you will wear it most.
What a sweatshirt is for after training
You come out of a session having sweated, often with wet hair, sometimes into a car park in February. The body cools fast, and that is where the stiff necks and colds that ruin the following week come from.
A loose sweatshirt over a dry t-shirt fixes that exact moment. It is a practical garment before it is a statement, even if the two go together well.
Picking a size
A sweatshirt is rarely bought close-fitting. It goes over another layer, it has to let the arms move, and it shrinks slightly on the first wash if there is cotton in it. If you are between two sizes, take the larger one: too tight across the shoulders cannot be fixed, slightly loose wears fine.
Making it last
Cold wash, inside out, no tumble dryer. The dryer is what kills a sweatshirt fastest: it shrinks the fabric, stiffens the inner face and tires the print. Pull the hood cords out before washing if you would rather they did not twist up inside.
What it goes with
It pairs with the streetwear range, which it shares an approach with: clothing that says you train without turning into a uniform. Training gear is in Brazilian jiu-jitsu gear.