I say yes. Liriano is a really good SP and at a price of $8 that is a steal. I like Stanton but I worry that he will be more Adam Dunn. His k rate worries me plus he doesn't have a track record in the majors. I think Stanton will be good but I will still take the more sure thing in Liriano.
"In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move."- Douglas Adams
I would take the Liriano side, it's a better value and Liriano's no slouch. Alvarez is a very similar player to Stanton in terms of what he'll give you (plus power, k's, low average). You don't need two of those type guys on your roster and Alvarez at $6 is a better value. That said, if you trade for Liriano, you'll be forced to keep 2 pitchers, which is never great. Not sure if you have any other bats, but o for me, it would be Choo, Werth, Alvarez, Liriano, and Buchholz.
My first inclination was to pass on this deal, but I think the other posters brought up good points with Alvarez v. Stanton. I would probably lean toward the good SP and gain a bit of savings in the process.