Love my new Acrylic Kohler Archer tub! We did our bathroom about 6 months ago, so it's had plenty of use to really compare it to our Cast Iron upstairs. I love long tubs with a good book. First thing I love that was noticeable right away: With my cast iron, I need to fill the tub before getting in, other wise my back absolutely freezes when I lie down and my skin hits the cast iron. With acrylic, it doesn't feel cold to the touch, the way cast iron does. Also, the Kohler archer has a special drain that allows you to get a really deep soak with a higher drain, which I love! No regrets with the acrylic, and no issues at all keeping it clean, either. Even with use daily, sometime multiple times.

I looked at several different brands of acrylic and acrylic-composite tubs. For me there was no choice, really, even though my plumber rallied hard for the acrylic (well duh, he didn't want to move the cast iron tub!) because I thought the acrylic ones LOOKED very plasticky and a bit fake, they lacked the authentic appearance of the iron tub. I would only use an acrylic if there was a serious weight issue with iron or you really wanted a jetted clawfoot tub. FWIW, the smallest acrylic clawfoot _I_ know of is 54". There IS a trick to getting the most heat out of a cast iron tub: do not mix the water to the correct temperature at the faucet. Fill the tub most of the way with hot water only, don't even bother turning on the cold tap, and let it stand for a few minutes to heat the iron. (Use this time to brush your teeth, make a cup of tea, whatever.) Then adjust the water temperature as needed with a little cold water and hop in. I get a good half hour before I have to add any hot water, and I like my baths searingly hot. However... A 48" clawfoot is awfully tiny - is there a space issue? Have you actually given a 48" the butt test? I can't see where it would be comfortable for anyone but a "little person" or a child (who would likely need a stepstool to get in), since the bottom of the bathing well is only 30" long! I'm only 5'2" and I can't get totally submerged in our 61" tub - if I stretch my legs out straight and put my feet flat against the end wall, the upper torso is out of the water and chilly (and our tub is nice and deep), if I scooch down to get my often-sore shoulders into the hot water my legs have to bend about 45 degrees. 5'9" DH is even more scrunched; if we do this again in the next house we're going to try to find a way to bump it up to a 66". If you're bent on a 48" and you're actually going to bathe in it, look for one with rim drillings (uses a deck mount faucet) or no faucet drillings (wall-mount or freestanding faucet) rather than a tub-wall drilling because the faucet will eat a good 2-3" of your foot space, and you get another 1.5-2" inches of water depth. (And if you use this nifty gadget on the overflow drain, you get another inch!)

OK, I know this thread is ancient but I just had to add my two cents worth for people who come along later as I did. The idea that cast iron retains heat longer than fiberglass or acrylic tub materials is simply a myth. Cast Iron, even with porcelain over it is a better CONDUCTOR of heat than any of the modern tub materials other than steel. Steel and cast iron will conduct heat at more or less the same rate with differences that would only matter in a lab. Cast Iron will transmit heat to the surrounding air and other materials faster than fiberglass or acrylic, which are both better insulators than cast iron. This is the exact opposite of retaining heat. Anybody who doubts this: Take a cast iron pan, fill it with hot water. Take a plastic pan of equal size and fill it with hot water of the same temperature. Put the pans side by side with a thermometer in them. Check them an hour later. I guarantee you the water in the cast iron pan has lost more heat and is colder because cast iron is much better able to radiate heat to the surrounding air than plastic. There is no way that any metal tub whether steel or cast iron is going to keep the water in it warmer than fiberglass or Acrylic will. Yes cast iron does radiate some of the heat from the water back to the bather above the water line, which some people like, but it does this because it's a better conductor of heat, not because it holds heat. The sole advantage of cast iron is, admittedly, much greater strength and if you want maximum strength steel is stronger still. I've demo'd multiple cast iron tubs into pieces with a sledge hammer. It shatters easily. Try that with steel.

My acrylic Bain Ultra air tub was set in a bed of mud with a piece of think plastic between the mud and tub. This was done for the ease of removing the tub if ever the need arises. It's as solid feeling on the bottom as my husband's Kohler cast iron tub. As for cleaning, that's a different story. You're not supposed to use anything abrasive on acrylic. Believe it or not, Scrubbing Bubbles is considered abrasive :( That's been my go to tub cleaner for years. To clean my acrylic tub RIGHT, I use Gel Gloss. It's a pain (literally!). You spray it on, let it sit, buff it and let it dry and then wipe the residue. When I'm in a pinch for time or physically limited, I will use Scrubbing Bubbles. There are very few non abrasive cleaners out there. One Bain Ultra suggested was Lemon scent Lysol. NOTHING works better than Scrubbing Bubbles!