The biggest differences between 18650 or 22-23 what ever cylindrical cell in li ion chem or lifepo is the cycle life and self life..
On this forum we have someone(forgot who, i am terribly sorry) that was squeezing out the last mA...... no, the last picoA out of a cell, he got ~1500 cycles.
Needles to say that with every cycle the cell "consume" itself like a steam engine(dendrite mostly).
There are forum members that use a 60% dod and after a 1000!!! cycles still have a 70% SOH..
Back to lifepo.
Some new cells can do at a 80% DOD 6000! cycles
So is it worth the money to rebuild your battery bank after 5 years in li ion becouse you had 1000 cycles? or spend 3 times more and gain 4000 cycles....
The overall price is the same.
BUT the ever irritating BUT...
With lifepo4 big capacity cells will save you A LOT of time.
In the end, price wise....it does NOT matter per kwh storage for one year or one cycle.
Heck li ion 18650's are in the long run cheaper....go big or go home.
With that i mean, make your ess big enough that you can last two weeks without sun and they will die of ageing and not cycle life...
(Many thanks Daromer for you giving me my homework, was some nice calculations)
With best regards Igor