I've done a lot of sound engineering.Personally I prefer to DI the amp,because that's what I'd want as a bassist.However,just as there are crap engineers out there,there are crap bassists who have no idea how to set their amp up,there are crap bass amps,and sometimes DI'ing the bass is simply a more practical option.Also,if you could hear your sound from the PA,bear in mind you're behind it and what it sounds like 20 metres in front will be very different. Sound waves from low frequencies are long.Simply ask your next engineer if he/she can DI the amp.If they say no,ask them why.And NEVER piss the engineer of, even if they're an incompetent twat,some of them are cynical bitter twisted people who are likely better connected than you are and can do serious damage to your reputation.....The voice of experience!