VoLTE support is on the way. But even so, I'm not sure I'd want an LTE-only device for the next few years. LTE is new enough that there must be areas with CDM

VoLTE support is on the way. But even so, I'm not sure I'd want an LTE-only device for the next few years. LTE is new enough that there must be areas with CDMA coverage but not LTE. The big advantage of VoLTE over a straight TCP/IP connection is a packet priority scheme that will give you latency guarantees for VoLTE that you can't get from SIP, so voice quality should be more consistent. Are you getting decent voice quality from SIP?