I agree both are positive ratings, but if a broker uses both terms, then a buy is always a stronger recommendation than an outperform. of course not all brokers use both or any of these terms (as you can see in the marketwatch list). The initial link in the OP clearly shows the heirachy of terms they were using.
p.s. sorry i forgot my sentiment settings in last post (first time using new format)
BDR Price at posting:
46.5¢ Sentiment: Buy Disclosure: Held