I had this exact decision to make a few weeks ago when my contract was up (imo these are the two best phones on the market atm), and for me the choice was easy. As a gnex owner for two straight years, I was personally looking for something different and exciting...
1. The G2's display isn't *that*much bigger than the gnex, so there's that. Yes it looks a lot better, but it's not an exciting enough jump in size from a near 5"phone.
2. While I love the idea of customizable soft keys and enjoyed them on the gnex, I think the capacitive buttons and home screen button make more sense. The bottom bezel is very small, and that's where the buttons reside, so no screen real estate is lost. Not only that, since they don't take up any of the display, you have to the option to choose soft key on- screen buttons (as soon as ROMs are developed), and simply turn off the capacitive buttons. With the G2 you're stuck with soft keys regardless of preference.
3. The s-pen is awesome. I'm an artist and I'm pretty amazed at the features of the included sketch app. The handwriting recognition is pretty amazing, and slew of other pen features is a huge plus.
4. Features like smart stay and especially split screen are INCREDIBLY useful and are a deal breaker. The single killer feature the G2 has is knock-on, but the n3 has a physical home button, so it's unnecessary...one simple push is all it takes. And you don't have to even like touchwiz... Get a custom launcher.
5. I'd rather have a removable battery and sd card expansion. I don't ever have to swap the battery out if I don't need to, but crucially the option *is* there. And 32 GB fixed non-removable storage in this day and age of crazy high digital media consumption is just substandard.
6. More RAM and better ways to use it. With that extra 1GB of RAM, more things can be running concurrently, and more apps can be cached which means they'll start instantly right where you left off. And with options like pen window and split screen, multi-taking is so intuitive and fun! Pen window alone is such a groundbreaking feature that I could now not live without.
So those are my personal reasons for choosing the note 3. Just my $0.02. Spend them wisely!