Personally, I'm a big advocate of the Kirk's
Plane Talk method and I find it quite useful in creating and expressing myself when soloing. But having said that, I also find improvising over scales useful also, especially when playing to Eric Clapton when he was with Cream. The blues scale (so simplistic in it's way) I find is great to play around with. I'm not particularly keen on the pentatonic scale though and find that I rarely use it.
But whether it be chord tones or scales, I believe if it moves me then I'll utilise it. If it doesn't, then I leave it out! Whatever works for any given application!