I've installed both a cast iron and an acrylic tub at home (two houses) in the last decade. The acrylic tub was actually harder to install - easier to move around, but required careful attention to support and bedding, whereas the cast iron one, though heavy and hard to move, was free standing. The acrylic is also a bit safer - a slip in that one is not fun, but the landing won't knock you out cold. A slip in a cast iron tub always ends with a hard, dangerous landing.
FWIW, I prefer the cast iron tub personally, even though it does take quite a bit more hot water due to the need to heat a lot of iron when filling, and with the hard landing properties. Just feels right. And for all those who want only a shower in their house - to each his or her own - but while I am happy to use a quick shower to clean or rinse myself when in need, there is nothing more comforting to my old and frequently aching muscles and joints than a long soak in a hot bath. I indulge at least once a week. My wife feels the same way - she frequently takes hour long baths. Comes out warmed to the bones and refreshed - and at our age, even the inevitable wrinkles from such a long soak are barely noticable additions to all our other sags and creases.