I'd speculate that it's generally easier for people to not decide and conserve their willpower, but we still gravitate towards ‘decision mode’ when about to do

I'd speculate that it's generally easier for people to not decide and conserve their willpower, but we still gravitate towards ‘decision mode’ when about to do something that looks irreversible. Two common cases: a) Easily reversible or just insignificant action, no commitment—you offer a free product or trial, or a paid service that could be easily cancelled. Long copy would turn on ‘decision mode’, but we may want to avoid that, so less info is probably better. Example: Lots of ‘Web 2.0’ services. b) Not easily reversible action—money are required up front, or you're upselling something to free users. Regular people (not yet fans of your product) are likely to consider different options in this case. Long and good copy, therefore, would present more and more reasons to pay. Example: Apple website. That said, I'd like to see a study too.