Comparing quality of SD upconversion

[jsteinhauer]

What do you look for specifically, if you are trying to compare how well one BD player unconverts SDDVDs to another, or if you are comparing a BD player to a SDDVD upconverting player for that matter? Is it something you just eyeball? This doesn't seem very objective, since almost everyone will start out biased toward the player with the better reputation. Oh, all other hardware (display, AVR) stay the same.