I have steel tanks. I feel that for the average diver with average physique, the steel 100 is the best all-around work-horse tank. But steel is expensive and takes more maintenance. If cost is an issue, there is absolutely nothing wrong with aluminum tanks. They are definitely less expensive, an AL80 is a reasonable size for most people. Maintenance is much less since aluminum corrosion is self-limiting, unlike rust that just keeps rotting away at the material.
I had aluminum from 1980 to about 1991, then I switched to DIN and HP steel 100's. My friend, with whom I've been diving since 1989, has always had aluminum.
If you get aluminum, get the new "natural finish" aluminum. It's a much better finish than painted.