I avoided bodysuits for years on the assumption they were glorified leotards, something that would dig in at the hip and need adjusting every time I stood up. What changed my mind was trying on a plain jersey one in a changing room out of curiosity more than hope, and finding it sat flat under a jumper all afternoon without a single tug. The idea of a onepiece top had put me off. The reality, in the right fabric, is closer to a good t-shirt that happens to stay put.
If you've never owned one, start with a long sleeved black bodysuit in a plain jersey, nothing boned, nothing lacy, just a round or square neck you can wear under things as easily as on its own. That version earns its place in rotation faster than anything with a fussy neckline, because it works under a blazer for work and under dungarees at the weekend without ever looking like underwear. Once you know your size and how a particular brand's gusset sits, you can branch into bodysuits with structure, but the plain one teaches you what you actually need from the shape before you spend money on anything cleverer.
Worn properly, a decent bodysuit should look much the same after twenty washes as it did on day one, which is where a lot of cheap ones fall apart, literally, around the gusset seams. Hand washing or a cool machine wash on a delicates bag keeps the stretch in the fabric for longer, and a tumble dryer is the quickest way to kill the elastane and leave you with something baggy at the chest and tight everywhere else within a month. The poppers at the base matter more than people expect from something that small. Metal snap fastenings that click firmly shut outlast the plastic ones, which warp with heat and come undone at exactly the wrong moment on a crowded train. A well made bodysuit uses a fabric with real weight to it, dense enough not to go see through when you sit down, with flat seams rather than ones that show a ridge under fitted trousers. A disappointing one feels thin between your fingers before you've even tried it on, and the gusset is cut too shallow, which you only discover once you've already paid for it.
Next time you pick one up, check the poppers first and the fabric weight second, because everything else about how it wears follows from those two things.