The PW206 series engines are truly renowned for sooting. Pratt has made great improvements in that area with the 207 series by rearranging the fuel nozzles. I think Rolls Royce did something like that on the C47 with some success.
Overall, P&W engines are extremely maintenance friendly. Pratt's customer service is second to none. If I had a choice in engine type, I would'nt have to give it a second thought.