The problem is BYD's LFP battery energy density is only 150 Wh/kg. Compared to 260 in something like a Tesla.
https://insideevs.com/news/668659/tesla-model-y-batteries-by...
The key sellig point here is the cost.
But personally it just seems so worth it. LFP has far greater cycle count than Li-ion. That the battery is going to last 4x longer or more is a huge factor for me. The net-energy (across the usable battery lifetime)/$ is so much vastly better that I'm happy in most applications dealing with the weight.
Sure, that's true in individual cell studies in lab, or stationary energy storage (aka, ESS), but not necessarily in moving vehicles, ie, EVs. CATL's cheap, inferior LFP would probably make more sense in storage.