Bigger screen is better for looking at maps though. If you're just collecting data and want the odd look at your power/speed/whatever then sure go smaller, but if you're navigating with it then the bigger screen is much nicer and since this is the GPS thread and not the bike computer thread...
Having used both I found the 1030 too big and cumbersome. Granted I'd like the 830 to be a smidge bigger but I've not had any problems navigating with it and reckon it's a pretty good compromise.
Yeah the 830 is the best Garmin around at the moment. All the benefits of the 1030 but much neater and smaller and a bit more affordable.