Woogoo,
I have a chipped P38 DSE and a cammed 3.9V8 RRC outside my front door, P38 daily driver, RRC weekend mess about car. They are very different to drive and ultimately if you cane the P38 there would be very little between them speed wise but one thing immediately noticeable is just how much torque the V8 has from down low.
The DSE is glacial slow when cold and even warm needs a good 1500 revs before anything at all happens and doesn't really get a move on until the turbo and chip do their stuff between 1800 and 2000. From there to the redline though its all good.
The V8 on the other hand just pulls like a train from 1000rpm with instant, intoxicating throttle response and a glorious burble. Once up and running it runs out of puff earlier than the diesel though.
Now thats a 3.9, admittedly it has a piper cam but that should only be bringing an otherwise untouched 150k engine back to spec.
The 4.6 is a different animal again and should be a snorting power house. I've watched youtube clips of Yank guys off roading 4.6's and you should see the things jump up rocks and hills on a surfeit of torque.
So I'd guess the one you drove is a duffer.