Let me first preface everything that I'm going to say with the "small sample size" caveat. Yes, this is a full season worth of data, but with defensive metrics, especially for catchers, it's best to use a full 3 years worth of data before deciding whether a catcher is good defensively or not.
That said, Swihart was not good defensively last year. As has already been mentioned, he was the worst catcher in baseball in DRS. He was also below average in pitch framing (-1.8 runs above average). He ranked 44 out of 72 qualified catchers. For comparison, Hanigan was 19th at 5.9 RAA.
The staff did have a better ERA pitching to Hanigan than they did pitching to Swihart. Kelly and Miley were a full run better pitching to Hanigan, while Porcello and Rodriguez were about .3 runs better. Interestingly enough, Buchholz did not pitch to Swihart last year. He pitched almost exclusively to Leon, with 4 games pitching to Hanigan.