Dell's Mini 10 offers the higher resolution video, although it might get small on a 10.1" screen. Audio won't be great on any of them from what I gather from reviews I've read, so headphones or a good external speaker set will be needed (a pain on the road). I have user experience with the Asus netbooks and the Toshiba 305 series and both were terrible for built in speakers. Sounded great on headphones or connected to the pa system. It might be a bit of a challenge trying to practice with headphones on but can be done. I think the netbook for the road is a great idea. Will you be running BIAB from the usb drive or from an internal drive? Will make a difference on hard drive size when making your decision.
Good luck.