This is true for many services you buy from other companies. The reputation of a giant is likely based on the top people in that company and sometimes based on the top people who were in that company years ago. Unless you are also a giant company you are probably getting junior people brought on to feed the pyramid. If you can find a smaller practice with smart people you will usually be better off

100%. Many boards think that by getting Goldman or Morgan you're covering your ass. They don't realize that unless you're atleast $1BN in size they really are not incentivized to do a thorough job. Why? Because M&A deals are priced off a % fee grid (50bps to ~2% depending on the deal). 2% on 580 doesn't shift the dial for Goldman.