I would expect you to get the same sort of coverage as the EE handset. Do you have the same issues indoor out and in different locations? Can you check the following settings..
Enable or Disable the 4G Connection
From the home screen, tap Apps.
Tap Mobile networks.
Tap Network mode.
Tap the preferred network mode: To connect with 4G when available, tap LTE/3G/2G (auto connect). To connect only with 3G and 2G, tap 3G/2G (auto connect). To connect only with 3G, tap 3G only. To connect only with 2G, tap 2G only.
If the issue persist it maybe worth trying a replacement SIM.