Re: US Nexus 6 work in Europe, more precisely in Portugal (3G, 4G, etc)
These are the frequencies the phone will handle:
2G Network GSM 850 / 900 / 1800 / 1900 - all models
CDMA 800 / 1900 - XT1103
3G Network HSDPA 800 / 850 / 900 / 1700 / 1800 / 1900 / 2100 - XT1100
HSDPA 850 / 900 / 1700 / 1900 / 2100 - XT1103
4G Network LTE 700 / 800 / 850 / 900 / 1800 / 2100 / 2600 TD-LTE 2500 - XT1100
(Bands 1, 3, 5, 7, 8, 9, 19, 20, 28, 41)
LTE 700 / 850 / 1700 / 1800 / 1900 / 2100 / 2600 TD-LTE 2500 - XT1103
(Bands 2, 3, 4, 5, 7, 12, 13, 17, 25, 26, 29, 41)
Check the carriers you're going to use to find out if either model will handle all the frequencies they all need.