I chose the 2TB hard drive.
A worthy upgrade? If you need the extra space, sure. Also, if you think you are gonna hit 1TB or close to it at some point, it saves you the trouble of having to chance it to a bigger one later on, which can be a PITA.
A good model? Im not exactly sure what you mean, but I have the Seagate in mine. It is very quiet and it works fine. I have had zero problems with it.
I think the upgrade from 1 to 2TB is fairly cheap compared to some of the other upgrades Apple offers. So if you've got the money - go for 2TB. I don't think you will regret it.