I'd just do some informal experimentation with each product you're considering. Even with UOA, you won't be able to draw any scientifically valid conclusions, but if you're anything like me (hey, you joined this ultimate oil geekfest forum too...), you'll have some fun and probably learn a couple things along the way too. Given that the two grades in question are pretty close to one another, you probably won't see much difference, either in UOAs or in subjective performance. You
might possibly see that newly exposed dry seal issue introducing syn to a older, dirtier engine. Another factor to consider is that coming from the extreme frozen north, unlike folks like me from the deep south, you may actually experience a meaningful benefit from using a 0w oil in the winter versus even a 5w. I use GC down here on the Gulf Coast, but it certainly isn't the cold cranking ability I'm after!
So my recommendation is that you run a few relatively short OCIs (long enough to generate meaningful UOA results, but short enough that you can also make meaningful comparisons), make some observations as to what you like in the results, and then pick whichever works best for you, your car, and your circumstances. In 2007, you'd really have to work at it to find a oil that was actually bad for your car (convenience store non-detergent SA oils come readily to mind...), so just have some fun working out what's right for you. As you've framed it, you're making a choice between good, better, and best.