The comparison is faulty because AM is a company and the other alternatives are hardware.
Why is that relevant, you ask? Well, AM will (hopefully) continuously renew itself and its strategy in order to keep earnings high, whereas the hardware simply gets outdated and earns progressively less and less as time goes along. So: buying hardware may earn you more in the short term, shares in AM may earn you more in the long term.
Comparison is NOT faulty. It is a comparison of "investment" (whether in hardware or a company) and "return" (whether mined bitcoins or dividends paid out as bitcoins). I think most people will agree that the value of hardware (GPU or ASICs) will generally depreciate over time, so that is a "known." The big unknown is AM, which as you point out is a company. We hope they will continuously renew itself, but anything can happen.
don't mean to burst your bubble, but yeah, it IS faulty. Everything in that list has a decelerating profit vector due to the fact that the hardware cannot be upgraded and has a definite lifespan (assuming hash rate increases over time - a pretty safe bet). The exception is AM, which not only mines using hardware like the other 3 examples, but
also sells hardware to others, effectively offloading the lifespan-based risk at a discount and keeping the instant profits, which are then redistributed to shareholders.
It's rather like comparing 3 fixed-rate CDs versus a growth stock during a time of inflation. The CDs will perform less and less over time, but the growth stock is not limited to the fixed return that the CDs are, even though both are affected the same by inflation. (inflation is analogous to hash rate in this example)