While it is generally known that TCP can be more battery-efficient for mobile VoIP compared to UDP, the extent of this improvement can be surprising. After switching my Android softphone (Bria) from UDP to TCP yesterday, I observed a significant difference. Typically, by 2:20 PM, my mobile phone battery would be around 50%; however, with TCP, it is now at 88%.
Regarding voice quality, I have not noticed any discernible difference between the two protocols.