I'd use the heavier weight...
This is funny to me, because there was a thread about oil weight going on a few days ago and some folks suggested using heavier weight oil and a couple dudes chime in with: "OOH, you people think you're smarter than the engineers who wrote the owners manual!"
The reason newer cars recommend 5-30 is because it is thinner and has less resistance. This yields slightly better fuel economy but does does not provide more protection for your engine.