I have used both. My metal tank has rusted out the bottom after about 10 to 12 years. My first rubbermaid had a horse step inside and cracked the bottom, would not warranty it. I use a 100 gal rubbermaid for my ponies. It works great and a heater is easy for the winter. I have a heater for it but winter here is just not that cold. My horses have a 150 gal metal tank. When I clean it there is also some rust in the bottom. I have two horses that like to put the front feet in it. I am not sure how long it will hold up. My plans for now is wait. I think the rubbermaid for the ponies will last for years. When the horses punch a hole in the metal one, or it rusts thru, I want to go in, built a concrete pad around when it goes and purchase a concrete tank. The price at the local feed store was the same as the metal. I could not turn it over to empty, but will use a drain in the bottom with a brush. With the pad, I can have the drain empty outside the paddock into a grass area. I can put a float in it to fill it. I don't think the freeze here will crack it. But can use heater if needed. And it is a bigger tank. (I might try fish, not sure.) I do have to put something in my tanks for the squirrels to climb out. More than once, I have had them fall in. Than the tank has to be emptied and cleaned.