I personally have always used a copper pot- I currently use the clawhammer 10 gallon still.
If you are going to use stainless I would suggest using as much copper as possible in the column- I would also pack the column with copper as well. Many folks (including small startups) use stainless pots with copper columns.
If you can afford copper go that route- if not go stainless and use as much copper as you can elsewhere.