Generally speaking the B230 engines are lighter in the block, have smaller crankshafts, with smaller main and rod bearings, and shorter pistons with an almost non-existent skirt, and thin rods. Not a typical Volvo engine to my mind, and I will never own another.
The B23/21 engines use the traditional stout crank, rods, and pistons, and are nearly unbreakable. But they are heavier.
If you want an engine to thrash, buy a B23E and do whatever you want to it. Probably the toughest four cylinder engine ever put in any car.