Both these sources are of some interest. However I'm not too sure that players would be happy with a black box method (the iteration) to calculate gradings. I can just envisage the thread on this forum if the Trueskills method was used. It is impractical to audit and would still be adjusting ones skill level in 2005 (say) based on the latest game this year (played by two other players). On the other hand I like the idea that I have a probability of being the world's strongest player
I used something very similar to the Brent approach many years ago for a club handicapping event. The obscurity of the calculations was a big turn off for members, despite the increased statistical reliability. Something simpler replaced it the next season.