I see a lot of post about saying stuff like the "Nexus 4 isn't a big leap over the GNex" or more to the point "Nexus 4 isn't as big a leap over the GNex as the GNex was over the Nexus S". I wanted to test that below so I have compared all three devices to show how the LG compares to the GNex, and to show the generational jump in each case.
Legend

NS = Nexus S, GN = Galaxy Nexus & LGN = Nexus 4

CPU

NS: 1GHz single-core ARM Cortex-A8
GN: 1.2GHz dual-core ARM Cortex-A9
LGN: 1.5GHz quad-core Krait

Bigger Leap: LGN
The quad-core Krait is a much bigger leap over the dual core A9 in all aspects. Although it is about a different chip based around Krait, the table on the link below shows how Krait is better than A9 in all areas, and also how little difference there was between A8 and A9

http://www.anandtech.com/show/5559/qualcom...25-benchmarks/2

GPU

NS: 200 MHz PowerVR SGX540
GN: 384 MHz PowerVR SGX540
LGN: Adreno 320

Bigger Leap: LGN
The Galaxy Nexus basically had an overclocked version of the same GPU the Nexus S had, the Adreno 320 pair with 4 Krait cores has been shown to wipe the floor with everything, including the Tegra chips.

http://www.trustedreviews.com/news/qualcom...and-exynos-4412

RAM

NS: 512MB
GN: 1GB
LGN: 2GB

Bigger Leap: Draw
Doubled each generation, no winner here.

Screen

NS: 800x400 4" SAMOLED (233 ppi)
GN: 1280x720 4.65" SAMOLED (316ppi)
LGN: 1280x768 4.7" IPS LCD (318ppi)

Bigger Leap: Draw
This was a difficult one. when you look at the numbers, it's hard to see why I didn't give this one to the Galaxy Nexus, the screen got a lot bigger, much higher resolution resulting in a much better PPI, which GN to LGN the numbers stay roughly the same, so hand down win for the GN right? Well, the LG IPS screen may be the same size and resolution, but the IPS screen is, light years ahead in quality, brightness and saturation than the Pentile SAMOLED screens Samsung uses. LG have been pushing screen tech forward and having held a normal LCD next to a SAMOLED and seen the difference, I can't wait to see what and IPS screen can do.

http://www.pocket-lint.com/news/47075/lg-o...-longer-battery

Battery

NS: 1,500 mAh Replaceable
GN: 1,750 mAh (LTE edition had 1,850 mAh) Replaceable
LGN: 2,100 mAh non-replaceable

Bigger Leap: LGN
The A8 to A9 core didn't bring that much power consumption reduction (if anything, the overclocked GPU made power consumption worse). Not only is the LGN bringing a much bigger capacity battery, but LG have also claimed to have created a battery that is 60% more efficient at the same capacity than it's competitors. Even if this claim is highly generous, the capacity leap alone gives this one to the LGN.

http://www.pocket-lint.com/news/47075/lg-o...-longer-battery

Rear Camera

NS: 5MP auto-focus, single LED flash, sub 720p video recording
GN: 5MP auto-focus, single LED flash, 1080p video recording
LGN: 8MP auto-focus, single LED flash, 1080p video recording

Bigger Leap: Draw
Unfortunately the cameras in the nexus phones have been nothing to brag about. The GN has been widely panned, and although the MP bump should bring improvements, the leaked photos from the LGN have been very lacklustre. There is hope, as LG have been shouting about their new sensor and the poor shots could be down to software / driver issues, but as of now, they are all pretty poor in light of the competition

http://www.techradar.com/news/phone-and-co...-camera-1096739

Front Camera

NS: VGA (640×480)
GN: 1.3MP, 720p video
LGN: 1.3MP, 720p video

Bigger Leap: GN
The Front facing cameras on the GN and LGN will be practically the same, while the leap from VGA to 720p on th e NS to GN provided a much needed boost for video calling.

Conclusion

It think it is safe to say three things:

a) The Nexus 4 will be a bigger improvement over the Galaxy Nexus, than the Galaxy Nexus was over the Nexus S
As the above shows, in every area that counts, the LGN is either as big of a generational leap, or bigger.

b) The Nexus 4 is a highly significant improvement over the Galaxy Nexus
Again, clearly seen above, the component improvements are leaps ahead of the Galaxy Nexus, and is a worthwhile upgrade.

c) The Nexus 4 will be an awesome phone
The specs above, coupled with stock Android 4.2? Yes Please! The design is subjective, and yes it may look a little boring, but under the hood, this phone has what it takes to be the best Android phone available. I personally love the design, and the subtle evolution from the Galaxy Nexus provides a brand, something that consumers can recognise.