Just got curious and dig some fast numbers: for the density looks like it’s closing:
for Li it’s 314 Ah x 3.2 V / 5.6 kg = 179 Wh/kg;
for Na it’s 210 Ah x 3.1 V / 4.7 kg = 138 Wh/kg.
But still it is ~ 20.8 Wh per Euro for Li vs 11.4 Wh per Euro for Na (Wistek, CN stock), let’s wait for some time.
And the extended voltage range is two sided sword: easier to find SOC, but it could be challenging to use all of the range for loads.
Still very scattered info on cold weather performance: some sources say it’s fine even up to -45 C, some limits to -20 C with seriously limited currents. And haven’t seen reliable info how bad it could be below these limits - if there is no permanent damage (except probably some loss of capacity), it’s game changer for outdoor off grid systems here.