A good sweatshirt suits almost anyone, which is part of why it's so easy to get wrong. If you want something to look polished the moment you put it on, this probably isn't it, a sweatshirt needs a bit of life in it, a good bag or a decent pair of boots to stop it reading as pyjamas. But if you're after something that sits comfortably through a long day, works under a coat, and doesn't need ironing or thinking about, it earns that place fast. Think twice if you're drawn to the very boxy, cropped styles and you're not keen on bulk around the middle, because the extra fabric pools exactly where you don't want it.
On colour, the ones that work hardest for me are the muted ones, a soft grey, a faded navy, an oatmeal that isn't quite cream. They wash well and they don't scream for attention, which means you can wear the same one three times in a fortnight and nobody clocks it. Bright primary colours and anything with a very stiff, glossy print tend to date fast and show marks within a wash or two, so if you're choosing between two otherwise similar ones, run your hand over the print and check it doesn't feel tacky or raised, because that's usually the first thing to crack. A slightly brushed, matte finish on the fabric also tells you it'll keep its shape rather than go bobbly and thin after a few washes, check that with your fingers before you check the mirror.
These earn their keep most in the cooler months, obviously, but the real value is in the in between weeks, the ones where it's too cold for a t shirt and too mild for a proper coat, worn with the sleeves pushed up on a walk or layered under a jacket for something that needs a bit more effort than loungewear but a lot less than a jumper. They're less at home anywhere that calls for tailoring. Pair one with a stiff blazer or anything structured and the two just argue with each other, the soft and the sharp don't sit well side by side. Chunky knitwear over the top does something similar, you end up looking padded rather than cosy.
What makes a good one worth reaching for isn't the cut at all, it's the neckline. A ribbed crew that sits close without digging in, that doesn't stretch out of shape by the second wear, is the detail that makes you grab that one over all the others hanging there.