I'd say the 4PRO for sheer flexibility. I've owned one before, and I've also had the SVT-CL. I really regret selling the 4PRO, it and my old SVP-Pro preamp was probably the best setup I've ever had. The SVT Classic had one decent sound, but zero flexibility. I'm a guy that likes one head to do a million things, as opposed to one amp for every task. The 4PRO accomplished a lot for a single amp!
Get the 4PRO.
Get the 4PRO.