FWIW, Addictive Drums alone is the full-blown package, and worth the price difference. The sounds are much more realistic and can be tailored much more than Session Drummer can achieve.
The TruePianos Amber I do not use often, but Dimension Pro has some very nice piano banks in it which I tend to default to more often. Again, the ability to tailor the sounds easily in Dimension Pro is the reason.
The AAS Strum Acoustic I have not used much, so cannot speak well to this, but their are videos on how to use it effectively.
There are videos on these items... check around in the
CakeTV area a bit.
Edit: The demo recommendations are very good ones! Even better than a video!