Now, if you've been an AT&T customer as long as I have, this download speed improvement is a much appreciated improvement. De la Vega also said that the LTE network has helped alleviate congestion on AT&T's older 3G and HSPA+ networks, which has improved the rate of dropped calls and overall performance of the 3G network. This is also good news, since as you know, AT&T hasn't had the best track record when it comes to dropped calls. So what does this mean for you and your decision? As you correctly noted in your question, the LG Nexus 4 does not support LTE. And the Samsung Galaxy S3 does. But as you also point out, the Nexus 4 has the latest version of Google's Android OS 4.2, aka Jelly Bean. Meanwhile, the Galaxy S3 on AT&T is still supporting the previous version of Android 4.0, aka Ice Cream Sandwich.
Personally, I think that the faster speed of the LTE network, which is supported on the Galaxy S3, trumps the software benefits of having a pure Google phone.This is especially true for AT&T customers such as yourself, As I pointed out above, the LTE speeds really are a marked improvement over AT&T's existing network speeds, What's more, the Galaxy S3 on AT&T is iphone screen protector with back button likely to get the upgrade to Jellybean sooner rather than later, Sprint's version of the same device already has gotten the update..
At any rate, I think the faster LTE network is worth the sacrifice of not having the latest Android software. I understand that some people may not like the software called TouchWiz that Samsung adds to its Android devices. There are many who prefer a pure Google Android experience. And I can understand their point. But I don't mind TouchWiz so much. Still, that is a consideration. If you prefer the pure Google experience, you won't be getting that with the Galaxy S3. But I really do think that for AT&T customers in particular, the lack of 4G LTE on the Nexus 4 is a deal-breaker.
T-Mobile has deployed a faster version of HSPA+ that offers theoretical download speeds of iphone screen protector with back button 42Mbps, AT&T's network tops out at a theoretical speed of 21Mbps, The Nexus 4 for T-Mobile supports the HSPA+ up to 42Mbps, So in theory, the Nexus 4 could operate at twice the rate of AT&T's version of the phone wherever T-Mobile supports HSPA+ 42Mbps, If you're an international wireless consumer, then LTE is also less relevant, since very few carriers around the world have deployed LTE so far, In that case, the Nexus 4's pure Google Android experience looks very attractive by comparison with the Galaxy S3, which in international versions doesn't support LTE..
Also, as you pointed out in your question, the Nexus 4 lacks a memory expansion slot. By contrast, the Galaxy S3 offers a micro-SD. While this is not a huge deal-breaker for me, if you plan on storing a lot of apps, music, pictures, video, or other media on your device, it's definitely something to consider. The Nexus 4 comes only with either 8GB or 16GB of internal storage, depending on the model you choose. And because it doesn't have the expansion slot, you can't add additional memory for storage. Meanwhile, the Galaxy S3 comes in three flavors with 16GB or 32GB of internal storage, as well as a 64GB version that is now offered in Europe. Because this device supports micro-SD, the storage can be expanded using 32GB and 64GB cards.