My Carlos Pena for his Jonathan O. Sanchez = net gain?

[Benkei]

Tough call, I already have a good pitching staff, but Sanchez would bump me up in ERA, WHIP and K/9 if he keeps performing like he has. I have more room to improve in our standings in hitting categories, but Pena is just rotting on my bench right now. It really comes down to whether or not Pena is underachieving and Sanchez is overachieving.

Here is the vital info:

12 team Roto League, deep rosters, keeper league, auction format but no salary cap ramifications on this one, both guys have pretty cheap contracts and are keeper eligible

I also have 1 unused reserve spot (transactions cost $2 per real money) that opened up due to Cruz recently going on my DL, which I could use to pick up the likes of Troy Glaus or Aubrey Huff if I jettisoned Pena

Hitting Cats = R, RBI, SB, OBP, SLG
Pitching Cats= W,S, ERA, WHIP, K/9

My roster:
Active Lineup
Hitters
Doumit, Ryan C
Mike Napoli C
Pujols, Albert 1B
Zobrist, Ben 2B
McGehee, Casey 3B
Jeter, Derek SS
Kendrick, Howard MI
Figgins, Chone CI
Fukudome, Kosuke OF
Soriano, Alfonso OF
Swisher, Nick OF
Pierre, Juan OF
Hamilton, Josh OF
Matsui, Hideki U

Pitchers
Capps, Matt P
Danks, John P
Hughes, Phil P
Pettite, Andy P
Kershaw, Clayton P
Contreras, Jose P
Wagner, Billy P
Weaver, Jered P
Wilson, Brian P

Reserves
Pena, Carlos
Francoeur, Jeff
Zito, Barry
Lewis, Colby

Injured Reserve
Cruz, Nelson
Johnson, Nick
Simon, Alfredo