Being nibbled for one damage by a single 1/1 Rat is often so inconsequential that it can be ignored, but even a few Rats dealing damage in the form of poison counters can be a real threat
Aetherflux Reservoir is a very unusual Artifact card with a casting cost of four generic mana, and is highlighted by Wizards of the Coast on their homepage
All these variables influence which method is best
Ebay A very small percentage of the cards I buy come from Ebay, and for collections in specific, the ratio is even less
Then, the last ability allows you to proliferate at the end of each turn, so long as a phyrexian died under your control
Also, even against decks with counterspells, resolving Sphinxs Revelation for two or three at the end of my own turn has been absurdly easy since theyre built to tap out to play Restoration Angel or Snapcaster targeting Azorius Charm at the end of my turn