If you read the sales blurb, the Scorpion isn't marketed as a contender to truckmounts at all! It's sold on the strength that it has a shed-load more airflow than any other portable.
I'd presume that the reason its pump is so noisy is because it's a 500psi monster (the latest model, anyway, which I presume is the one in question). That's quite a lot different from a lot of other portable machines.
If you think about it for a minute, there's probably some very good reasons why the machine in general is so noisy. Firstly it has one more vacuum motor than most portables. They're configured in parallel aren't they? I think it has separate exhaust ports so as not to restrict the airflow on the way out of the machine, to get every last cfm out of it as possible.
Yes it's ugly, no s**t! But who cares? a Kohler petrol engine isn't exactly a work of art

Customers don't inspect your machine, they look at the item you've been cleaning.