Hi Carlos.
Yes, I would definitely encode at a higher rate for the iPhone or iPod Touch as the screens are very good on those devices. Much better than the iPod classic or iPod Nano in terms of size.
So, I would recommend encoding 16:9 video at 640x360 @ 1200kbps for the video. Personally, I use 96kbps AAC stereo for the audio.
Good luck!
Jon
TreeLine Productions
Fort Collins, CO USA
Currently producing these popular podcasts:
"The Rest of Everest" Video Podcast *Voted as one of iTunes' "Best of 2006" & "Best of 2007 Classics" podcasts
*Nominated for "Best Video Podcast" in the 2007 People's Choice Podcast Awards
www.therestofeverest.com
"Beyond the Movement: The Pilates Podcast"
www.thepilatespodcast.com