I think out of those, Newton 2 is probably the easiest. AHG doesn't actually smooth the track, just heartlines it for you. I haven't really had very much luck with AHG. If you use Newton 2, your first few tracks will probably appear to be what people like to call "Newtony" and it is very easy to adjust the sliders and go with the result just because it's smooth and looks kinda cool, but also frowned upon. FVD++ is more confusing to use than Newton but it can do some things that Newton can't, like perfectly smooth banking transitions into and from straight segments.
Newton 2 tutorials:
http://www.youtube.com/playlist?list=PLC1820F7CD8DB9335
Feel free to do what you want, but I personally would not use Newton for wooden coasters unless it's a Rocky Mountain or Intamin prefab. FVD++, maybe, but probably use mostly geometric segments.