Ever since after the Nexus S, Google decided/pretty much stated they will not implant external microsd card slot due to wanting more control over security in the phone as having external microsd cards doesn't give full permission/control over it, wanting to encourage users to use the cloud for external storage(though this isn't best ideal for everyone like for those who majority have data limits or slow speeds), and not to confuse users with the storage. More explanation about no sd card can be read at below link.
http://www.androidpolice.com/2012/10/30/matias-duarte-answers-questions-about-jelly-bean-ui-and-the-lack-of-micro-sd-cards/
As for the LTE, the only explanation why this isn't there at the moment though may change in the future is due to Google not liking the limitations/restrictions carriers ask of Google (there are speculations the SoC on the Nexus 4 supports LTE though not active when launched).
One example; take a look at how Verizion did the Galaxy Nexus with the updates(and adding Verizion bloatware) compared to the GSM Galaxy Nexus, the update for jellybean(4.1) on the GSM Galaxy Nexus was pushed out in the second week of July after the Google IO event while the Galaxy Nexus on Verizion's network update was pushed on the last week of Sept(three months for the update it took on Verizon's Galaxy Nexus).
Sources:
http://www.gsmarena.com/android_41_jelly_bean_rolling_out_to_gsm_galaxy_nexus-news-4502.php
http://www.engadget.com/2012/09/21/verizon-galaxy-nexus-finally-lands-jelly-bean-update/
Now for the thoughts of the cosmetics with the Nexus 4 is a personal preference though the build quality is no doubt improved over the Galaxy Nexus acordding to one of the first few hands-on/review of the Nexus 4.
http://www.theverge.com/2012/11/2/3589280/google-nexus-4-review
Lastly, the non-removable back is another personal preference which is not going to be a deal breaker for everyone.
Personally, I am completely fine/go through the whole day with my stock battery that came with the Galaxy Nexus though if I require a lot more battery usage like on a trip or if I'm not going to be near a wall outlet for a bit, I just simply use a mobile battery charger on to go which I would plug it in with the phone to the external battery/charger and leave it in the bag or pocket as it's quite small and isn't a hassle to carry around with.
http://www.amazon.com/gp/product/B005K7192G/ref=noref?ie=UTF8&psc=1&s=wireless
If the Nexus 10 had a quad core instead of the CPU that currently implanted, the resolution of it would not be the same because at the time being, there is no other CPU that supports the Nexus 10's resolution of 2500 x 1600 beside the Exynos 5250 which is what the Nexus 10 runs by.
Although it's a dual core, the 1.7 Ghz Cortex-A15 and the Mali-T604 performs better than the Tegra 3.
CPU wised is 15-20% better while the GPU is able to easily beat the Adreno 320 so Mali-T604>Adreno 320>Tegra 3.
More info/Source:
http://www.androidauthority.com/arm-a9-vs-arm-a15-87559/
Now if you excuse me, time to play some League! ;D!