I have both programs and have used both for about a year. By FAR, I use Elements more that Pinnacle. Elements has just about everything you will need at a begginer level. Also, IMHO it is much easier to use than Pinnacle. The only advantage I see Pinnacle has over Elements is the DVD authoring portion but, that is very minor. Elements does an adequate job there as well. Pinnacle also renders a little faster when burning to DVD but, that is a convenience and not really a quality factor. Most transitions, effects, tweaks, adjustments, etc. that I have needed I have been able to accomplish in Elements.
As far as instability goes I have had some issued with Elements but, nothing severe. Also Elements has audio transitons, noise reduction etc. I believe Pinnacle has the smart soudn you were talking about but I have never used it so I cannot comment one way or the other.
Anyway, I would recoment Elements for the money. Like you mentioned, you may be able to get a lot more with Pinnacle but, you will pay for it. Good Luck.