OK, he's not, but he is a metallurgist and a homebrewer,
when i took metallurgy in college i was pulling down a 3.8. i am an engineer and a homebrewer but not a god nor a metallurgist.
my point is this. when i was first starting out i bought quite a few things i wish someone has told me different on because i ended up just wasting money.
to answer the question: stainless vs enamel i would not choose enamel.
when i first started out i too was warned about aluminum. but as i reaserched the topic both on forums, books, and fda reports i have come to the conclusion that the aluminum urban legend is a bunch of bunk.
again it's your money and you can spend it any way you wish. i would say though that if you have even a remote desire to cultivate this hobby, buy smart.