Our company believes that use of Config 3 saves 20kg of fuel and it is the SOP landing configuration. It turns out that this fuel saving is only happens if you are fully configured for landing at 13 miles. Most of the final approaches on our route network don't come anywhere close to a 13 mile final (notwithstanding the rare and weird 30nm final
). It seems to me an accountant's fudge; as any fule no, how the approach is flown from top of drop makes more difference than any flap configuration.
As mcdhu says, thrust is not one of our stable criteria; it used to be, but the Autothrust seems to almost hunt for the correct power setting in Config 3, which is probably why the requirement for thrust was removed – it's just not necessarily there at 500'!