It all depends on whether or not you believe that certain pitching situations have more "leverage" than others and trust simmy to get the guy you want in at the right time. For example, you are up by one and your opponent has his 3-4-5 hitters coming up in the 8th, do you want your closer to go in the 8th, or give that to your set-up guy, and can you be confident you'll get what you want with the settings available?
Personally, I'd rather make sure by best relievers get as many innings as possible over the course of the season. The higher the STA, the more innings he can pitch (of course) so if he only gets 70 IP as a closer, but is capable of pitching 100+ IP as a set-up, you have to decide where you'll get the most production.