It really is a personal preference... If you want to use voice and data at the same time, you should select voice and data so you can talk & surf while on LTE... Verizon's voice calls fall back to the legacy 3G CDMA network where there is no LTE or VoLTE has been opted out of by the user... and you can't talk and surf on cellular only on Verizon's 3G network...you have to have wifi for data.