I agree with Peter.
We discussed this issue at length from a S American perspective at pp36-40 of this paper:
http://www.proaves.org/wp-content/u...-y-Splits-Conservacion-Colombiana-23-3-48.pdf
Even taking into account the "scoring system" of HBW, the biggest difference between committees can be analysed in terms of proactiveness (which can be looked at from a 'glass half empty' perspective as laziness). But in fact, they are all pretty much the same in coming to a list and being broadly very poor at updating that when new research comes along. All of them....
The least proactive of them all is H&M, in the sense that it is published irregularly on paper, although that may change in future.
The most questionable of them all from a birder and conservationist perspective - in terms of the committee wasting huge amounts of time and proposals on utter trivia (vernacular name hyphens, subfamilies, splitting hairs on Latin name spellings etc) whilst being essentially pretty lazy on more pressing issues (e.g. peer reviewed papers proposing changes to species limits) is AOU, and especially SACC.
The laziest of them all - in terms of online lists - are then Clements, who wait for the rather priority-misguided SACC or annually updated NACC before acting themselves.
IOC are the best at keeping up to date with latest papers. However, it's quite odd and entirely inconsistent, when you think of all the edgy calls and novel taxonomies that IOC took up when originally established, that they have essentially ignored HBW splits and called their list sacrosanct on that front.
And it's not like HBW have done a good job at all at correcting the multiple unjustifiable splits in their list that have been widely written about in groups such as Ramphastos, Aulacorhynchus, Coeligena and Oxyura. Again, they came to a final list and when that has been shown to be wrong, continue to cling to unjustified dodgy splits in the same way that SACC [and, therefore, by extension H&M and Clements] have such a strong track record of clinging desperately to unjustified dodgy lumps.
When looked at in those terms, all the lists suffer from too much pride in a product as at a particular point in time and a lack of openness or energy to do the best possible job at keeping a rational taxonomy, in all cases hiding behind spurious arguments about either being conservative or waiting for new data (or in the case of "the rest vs HBW", attacking the process as a tool conveniently to ignore the mostly correct outcomes). Promoting conservatism in checklists is promoting irrationality since it promotes ignoring new published research or new ideas. We have a situation where IOC, for example, broadly accepted most field guide splits when established but has broadly rejected all HBW splits which have the same status. It is difficult to come up with a rationale for that.
We really need one checklist, not four, which has its sole mission of promoting rationality and currency based on latest research, analysed on an objective basis. Currently, efforts are split across unnecessarily numerous incompletely updated and sub-optimal taxonomies, which serves no one any good.