2009 BH G4 frameset VS 2011 Tarmac SL2

[nexus1001]

I know this request can seem strange but I have an opportunity to upgrade my existing bike (a 2011 Tarmac comp SL2)
for a BH G4 frame.
I am wondering how a top of the line older carbon frameset (the BH G4) matches agains a very recent middle of the road frameset (the specialized tarmac SL2)
Any help would be immensely appreciated; I am primarily looking for info/insight on stiffness/handling but any other info would be useful!
thanks

 

[Philbo1]

I've ridden the tarmac SL1, not worth it. The SL2 is too stiff, not comfortable, not as light as the G4. I bought the G4, and it is an amazing bike. Test ride a G4 and find out.