Asymmetric risk is the most important consideration.

Sure, but the risk comparison is not T-Bills versus SPY, it's Berkshire vs SPY, yes? Single stock vs the US market of stocks.

Spot on with the post length :) Apologies !

As for BERK vs. S&P again, asymmetric risk. You've had a solid bull market. You have one vehicle (SPY) with a 99.95% upside exposure...vs. another vehicle (BRKB) with a third of the company and half the book in cash. If you think trees grow to the sky there's absolutely no reason to own Berkshire here. Or..is there?

DESPITE having substantially less EXPOSURE--Berkshire ACTUALLY BEAT the all-in, 99.95% all stocks S&P 500 the past 5 years!

5 years through Friday:

Berkshire Total return: 83.27% Annualized 12.88%

S&P 500 71.74% Annualized 11.39%

One hand tied behind its back--massive cash drag--no problem for Berkshire.

I'm still more concerned about the next 5 years and risk adjusted returns and optionality. The problem again is --I still don't know what will happen. So, Berkshire gives me a nice shot at some growth, some insurance against currency debasement and nice protection if things fall apart. What do you think happens to SPY in panic and turmoil?