IMHO: Used appropriately, Pruning and Trimming are both great tools for maximizing bud sites, flower size, and light penetration especially when growing in tight spaces. It also helps maintain overall plant health and vigor through every phase of growth. (with the exception of seedlings... obviously)
But I also think these practices should be used subjectively. I mean, if you're growing 1 foot tall plants in a stealth PC setup using CFLs then yea, every fan leaf might be more useful staying on your plant. But if you're growing a 5 foot tall heavily trained plant under HIDs, then removing some fan leaves from a branch may pay off if it means a once hidden bud site will now be getting direct light. And to be even more specific to my experience, growing a SCROG with a very dense canopy in very tight quarters, the payoff is a no brainer when comparing a bud site that's hidden by large fan leaves that can't be tucked under anything... vs. removing those fan leaves and getting direct light to that top.
I'd like to add that I once was a vehement advocate for never trimming healthy fan leaves, but have since changed my tune. Experience is the determining factor here, you've either seen the benefits yourself, or you haven't, period.