The bigger screen is nice without a doubt. This is pure visuals and not taking into account ergonomics. Sharpness is there with the 720p, but perhaps some of that feel is missing due to poor color calibration. However from what I've read it's really a calibration issue. Walking around the AT&T store, the LG Optimus G looks nice. It's better calibrated. There's color controls with the Nexus 4 kernel, and some custom kernels already have a color tuning app associated. The GNex wasn't well calibrated and so were all the Nexus phones before. However, I do have a calibrated Nexus S and it looks gorgeous. Better than my SAMOLED+ SGS2. While I still believe Google needs to provide out of the box functionality with proper calibration, all hope isn't lost because we can hopefully get that ability soon.
I'd also like to see objective display reviews. How good is the display itself? I know SAMOLED lovers always go "oh damn LCD is washed out it's DOOOOOMED." Remember that Apple got around crappy calibration by having a bright screen. The 4 and 4S looked good supposedly even with 65% of gamut only. I'm going to hope that I can adjust the colors on my screen soon so it looks half decent.
But to be honest I think I'm losing my pickiness with colors. I work long hours now and it's at a pathetic TN panel or laptop screen. I'm probably going colorblind. I spend little time in front of my Dell 27" at home now, but everytime I do I'm reminded of how nice LCD displays can look.
Gnex looks laggy. I'm not sure why. But remember Android runs background apps, and while you and I and other tech geeks might not install every app in the world, standard users don't care. They have so many things running in the background, syncing, it doesn't feel well.
Sorry

but I think the phone still is the best on the Android platform and having both the iPhone and Nexus, I can say you can't go wrong with either.
I'm a photographer and so I demand quality photo reviews. That's why I've never really dived into them before. I just offer a few subjective conclusions based on my observations. The camera is difficult to use and while the whole touch circle menu is "cool" it's less useful than one might think. It's too easy to select the wrong thing. Gimmick feature if you may.
In day, it's great. Indoors it's not as great. This is partly software and hardware. I think the iPhone limits the shutter speed and then bumps you to a higher ISO at a certain point. I had so many blurry photos on my Nexus it was't funny. I was TRYING to hold it still too. On the iPhone I didn't care and casually held it with 1 hand and snapped away with pretty sharp photos.
The part that bugs me is I feel like my SGS2 might give better photos. The Nexus line has been disappointing in photos, and no matter what the apologists say about how this is a development phone not a fun phone, stop it. First there's excuses for why the GNex didn't go quad and it went dual and it's not meant to be a powerhouse. Now the Nexus 4 changes that by having the fastest damn CPU in a phone. Let's not forget the Nexus S had a damn good camera for its time because the SGS phones of that generation led with only the iPhone 4 being better.
I don't see how an SGS3 is better than a Nexus 4. Maybe if you really love the SAMOLED display, but while my eyes like it more, I think the Nexus' display isn't bad. The fact that you can run stock AOSP Android straight out of the box is 100x more important. I'd NEVER run Touchwiz or Sense or any of that junk. That's half the reason why those phones feel like lagfests. Sense might have worked well for the ARM11 phones like the Droid Eris making it feel faster than the Motorola Droid in terms of scrolling smoothness. However they're all so bloated now that they contribute to a huge slowdown.
When my GF picked up my SGS2 she woudl always comment on how fast it is. This is with the broken hwcomposer on CM10. It's not even butter yet. I recall her SGS3 being great when she first got it but when I paid close attention to it last weekend it lagged like no other. Scrolling through a list on Foursquare was a horrible. It may be that I'm spoiled carrying two fast as hell phones, but I wanted to say even my SGS2 wouldn't do that?