I would take Wowitka. Seidenberg is two years older and still has not managed to crack the Flyers roster. Plus Woywitka has more size, leadership and hopefully gritty play.
Right now Seidenberg is a much better player. This is Woywitka's first year playing with adults though, so it is natural that he wouldnt jump in and start kicking @ss right off the get go. He has much higher potential. But Seidenberg has been better at both ends of the ice this year. Much better in fact. He was able to crack the line up last year, and would be our 7th defenseman (ahead of Woywitka, but behind Vandermeer because of his size) if it werent for Pitkanen.