An explanation of Football Outsiders' advanced statistics.
www.footballoutsiders.com
You can disagree with the efficiency or relevance as a 'rating system', but it is not subjective. It's no different than something like passer rating or rate+, it applies the same objective statistics to the same formula every time. It's just a bit more complicated.
For the record, I don't like the formula used for DVOA, or the formula used for passer rating. I think they both suck really, both for different reasons.
For DVOA, my main gripe is with where they draw the line on considering a play a "success", which is the very fundamental part of the formula. "On first down, a play is considered a success if it gains 45 percent of needed yards; on second down, a play needs to gain 60 percent of needed yards; on third or fourth down, only gaining a new first down is considered success." Just seems arbitrary, I don't know.
I don't like passer rating mainly because its naturally an inflationary statistic.
Both are indeed objective though.