Hi,
When I bought 40 x 200Ah in 2016, it cost me $8000 + $250 shipping. The price for the same capacity in LiFePO4 was about $8000, for Winston cells, but slightly less for shipping. I looked at the possible life of the two, and decided on NiFe.
Of course that hasn't worked out as I planned, and 7 of them have failed after 4 years, the others have lost some efficiency. I was getting 80%, now 50%, but that will be partly due to having less cells in service. They may all eventually fail. I haven't read of others having the same issue, so it appears to be rare.
I'm buying LiFePO4 this time. The 280Ah EVE cells seem to be a good buy. I'm getting 18 shortly.
In discussion with the NiFe seller about replacement/refund.
dRdoS7