He must have had a bad one - the M57 engine is known around the world as a first rate engine and has won international engine of the year on more than one occasion and has been in continuous production for 18 years now. Fuel economy is brilliant - under 10 L/100 pulling a brick shaped 2.5 tonne vehicle around.
Power was modest on the early units (130KW and 390Nm) but far from low and from the mid 2000's it has steadily increased in power and economy, while maintaining bulletproof reliability. They were dropped from the L322 in 2007 after Ford bought Land Rover.
While the TDV6 is a much newer and quieter design, the M57 is silky smooth in its power delivery. I also wouldn't call them unbelievable noisy - the engine fan produces a bit of noise but the engine itself isn't loud by any stretch - it sounds like you're talking about a 4BD1T the way you are going on. :D
He either had a dud - which is very rare, or the info you have is second hand and very far from the actual reality of these engines. I bet anyone here that owns/has owned one will strongly disagree with you.
The early L322's are known for having a dog of a transmission, but the engine has always been regarded as a gem.

