Is it worth going for the 4G Cel-Fi given that the price difference isn't huge? As it's a newer model my guess is that the electronics may have improved and I notice the coverage has gone from 600 m2 for the 3G version to 900 m2 for the 4G version (still not enough though).

Given the signal level, is it likely that an external aerial will be needed?

I couldn't see any feedback on how good they are. Does anyone have experience of them at home/work?

Background.

Have 4G signal outside at -118 dBm, go 500 m in any direction and that increases to around -109 dBm. Inside this drops to HSPA 14.4 Mbps and is at a level that will often drop calls. (All networks signals are bad at the houses around me, not just 2Degrees. Might be some big trees interfering.)