"Peter Sadler Transport" is Prim's trading name. He chose this name originally as PST is a trucking company, and initially tried to play OpenTTD with trucks/buses only.
He promised a fleet of
2000 trucks, and has yet to deliver on that promise!

Profit is probably the best indicator - but then again Connex also made a profit.

Each station of PST was at poor or very poor rating, yet his trains were generating
$200,000 per trip, because of the length of his trains, and sheer distance they were travelling. Essentially, you don't have to provide a good service to generate heaps of money. However, if someone else built a competing route, they'd steal all his traffic.
I think the game actually uses Company Rating, not just profit,
which has a number of factors. This gets displayed at 2050, who the game thinks won.