Generally speaking RHP have more success in the 80's game than do LHP, especially when talking about SP. Therefore I would suggest Sutcliffe over Burns, especially knowing that you already have two LH SP in your rotation already.
Burns over Sutcliffe, unless you can get the '84 version of Sutcliffe. Sutcliffe is over priced because of the big year I think and Burns can be used all 5 years (some are better than others) depending on the park, division etc. But then people know I am not afriad of lefies and generally have 3 lefties starting.