Will,
I just don't know where to start...
Having OWNED a 350 gasser, a Banks Powered 460, a V10, as well as Cat 3126 and our current Cummins ISL, all I can say is...umm, ok. :B
I will say I 100% believe your seat of the pants evaluation, and here's why; noise sounds and feels fast. Meaning, I think you'll find the V10 isn't as fast as it feels and the diesel isn't as slow as it feels. The excessive noise of the V10 makes it feel fast, the quietness of the diesel makes it feel slow.
Our current MH is actually quick off the line, but you have to pay attention. Diesels are drive-by-wire so there is a slight delay from the time you step on it until it reacts. Once it reacts you're all good.
Once moving there is simply no comparison. Hills that used to bring the V10 to it's knees the diesel just cruises up. The other thing to keep in mind, you said you drove a new one; diesels don't start to wake up until they get some miles on them.
Oh yeah, your info on the exhaust brake is a bit flawed too. Yes, some only have an exhaust brake, many have a true Jake Brake. Look up the differences. The gassers only have a transmission brake. The engine itself isn't controlling it, the transmission is.
Either way, I'm glad you're happy with yours and it's serving you well.