If leak is a concern, get a stainless steel tank with plastic top. They fit snuggly and no leaks. Most of my stainless steel ones leak JUST A LITTLE. Not enough to be a problem though.

This is one of the area if you ask enough people, you'll see a good split of opinions. The bottom line is, use what works for you. (which you wouldn't know without trying both....) There are strong opinions on both sides and there are pros and cons. You won't find "the best" unless you try yourself.