Color films for Fall colors are Kodak Ultracolor 160 [35mm], Ultracolor 400 [35mm], Portra Vivid Color 160, Portra Vivid Color 400, Ektar 100.
If you could get your hands on some Kodachrome I would go for it. If not, I would pick up some Elite Chrome.
I have had pretty bad lab prints made with Ektar 100. I have also had had great results. The cyan color is a problem though. When I get into color it will be a true test of film.
I have only gotten cyan skies when I scanned a perfectly healthy negative. Period.
If I was to use Provia, is it a true 100 speed film? I've seen posts where people talk about the true speed of films, such as Delta 3200 being closer to 1250. Is the only way to determine the true speed experimentation or is there a chart somewhere?
I would choose my film based on how I was going to get prints. Using slide film you will almost certainly be getting digital prints, or just scanned images. You could also spring for Ilfochrome, but it's hard to find and now inexpensive.
If you go for a negative film you will have a lot more printing choices, and they will be less costly. Also, keep in mind that slide film has a limited latitude. Negative film will be more forgiving. If you must shoot during the day when the contrast is high, I would skip the slide film. I am finding I am shooting less and less slide, and more negatives. The fact that my results have improved is the driving force for this.
For extra "punch" I have used a Didymium "enhancing" (red) filter, but the straight film properly exposed is practically as good.:)
Judging the palate of chrome films is very subjective however, and shooting a variety for yourself to see what you like is my very best recommendation.