Slide film-

Kodak E100GX is perfect for fall colors IMHO, but it was just discontinued. E100G is also excellent, just a little cooler balance and would be my recommendation. E100VS is warmer balanced, but higher contrast. In the right setting it could work really well.

That said, I've shot fall color on Provia 100F and Astia 100F too. I think Astia does a nice job with the yellow leaves, but the blue sky is not its strength. Provia has a slightly cool look to it.

Color negative-

I also find the new Ektar to be a little weird. I can't put my finger on it exactly, but red/orange look a little strange and blue tends toward an electric cyan. I've used Portra 160 NC, VC and Pro160S with fall colors with success.

I'm planning to shoot this fall on 4X5 E100G, E100VS, Portra 160VC and E100GX on 35mm (I have a stockpile).