Here is the way I see it... Pros and Cons of both... Its fairly, fairly close:
Raised his average 30 points from '08 to '09 despite striking out more
Basically a lock for 40HR and 100RBI while also scoring 90-100 times
If you count BB he is a huge boost, as he will BB around 100+ times
If you count Ks, he will kill you
Not quite sure if I believe the 30 Pt rise in average, would look for it to settle back into the .235-.245 range
Since joining Tampa he has been a stud, and a lock for 30+HR and 100+ RBI
Hits in the all around better lineup of the two
Should hit for a better average, even if slim, then Dunn
Since joing the AL East his average has dropped each of his 3 years, steadily
Like Dunn has a big time K rate
Doesn't walk as consistently as Dunn
Has never in his career had more then 490 ABs in one year
Overall the type of hitter you are going with is the pure power bat, both K a ton, both walk at a good clip, both have averages that if you don't have a couple .300 bats to balance them out will kill a team average, but both are locks for 30HR/100RBI. Pena has the better lineup, but Dunn has out produced Pena the last three years (since Pena has had a complete lock on a 1B job). I think personally I would rather have Dunn for 3 major reasons, 1. He will out right out produce Pena on any given year in R, HR, RBI and at the rate Pena is going also in Average and 2. Dunn is an ox, hes a lock for 540-560 ABs and pretty much has been since he came into the league and 3. The most important to me is the position eligibility Dunn carries over Pena. Buchholz could be a break out candidate, but with your staff I think its say to say that you wouldn't be hurt by losing him.
Id do the deal...
Great thanks to soto for the sweet sig!...