Since you want to model "newer" equipment, I would go with the largest radius possible that will work for your trackplan and layout area. I am not familiar w/ N scale equipment, however, the same applies to HO when you are using newer, larger 6 axle engines and longer rolling stock. Even though a manufacturer will specify the "Minimum Radius" this is usually the absolute min that the equipment will traverse. Any minor glitches is trackwork or equip can cause you nothing but troubles. besides, "cramming" large pieces around tight turns, even though it may work, just doesn't look very good.
I know you are fairly new to this, it may be a good idea to let us know the parameters of the layout you would like to build. An over view of the layout purpose, yards and yard configuration, staging operational and switching posibilities required etc. These are all things to consider in your trackplan. Even the best thought out trackplan will be modified as you build or later as you actually run the RR. This is the best time to do all your research and eliminate many of the mistakes that you would end up with.
