When Google releases a Software update, the GSM versions get it immediately. The Verizon and Sprint versions do not. The Verizon version never received versions 4.1.2, 4.2, or 4.2.1. The Sprint version still is on 4.2.1 and hasn't received 4.2.2. Plus there's the whole Google Wallet fiasco.
They'll have to once VoLTE goes into effect due to the Block C provisions in place on the 700MHz spectrum they purchased to run their LTE network. Provisions state they have to allow any device compatible with the frequency onto their network (Assuming they pay their bill). The reason this hasn't happened yet is because phones still need the CDMA network for voice and text, and thus can be restricted.
True, but the stock android will yield a little more storage space with all the carrier and touchwiz bloat removed. 16GB Nexus 4 comes with about 13GB of open space instead of 9GB on the Touchwiz GS4