I have limited experience with steel and Al, but I remember the rides between the day I sold my old steel HT and the day I rode my new Al HT. Night and day in ride experience. Steel is much more compliant and absorbs vibration better than Al. Al is generally stiffer and transfers power better.
I'd say that steel is more comfortable. It would make a better trail bike. Al is lighter and more rigid and would make a better race bike.
There are a lot of builders making frames of both materials, but Steel is harder to come by these days. Some mfrs might be Strong, Cove, Salsa, Canyon, Sycip, Surly, Kona and Jamis. Almost all other manufacturers make Al HT frames.
As far as value goes, you'll have more buying power with a complete bike than from a custom frame mfr but you also get a more "generic" bike.
Personally, I'd get a Cove...but that's just me. Steel is real!