I would get the 30 gallon Blichmann. That way you have a buffer if you decide to step up to 20 gallons in the future. The morebeer pots are nice, but I really like the sight glass and width to height ratio of the Blichmanns.
Right now, I do 15 gallon batches in a 20 gallon Blichmann. I use fermcap and scoop the foop.
I was a little nervous the first time I tried it. I will eventually upgrade to the 30 gallon, or maybe the 55....