FWIW, I've ridden with both and can tell you the biggest difference that I noticed other than the extremely funny and nice, yet incompetent track marshall, is that TPM seems more like a bunch of friends out riding. No regard for others safety and it seemed like everyone just wanted to be the fastest guy.
Don't get me wrong, you get that in every Org, but its almost encouraged to a point there.
Here's my experience. Summit Point, Shenendoah, coming down the main straight tailing a CR, he lets off the gas completely and sits up just before turn 1...i just about a$$-pack him, end up diving to the inside and almost ran him off the track.
Drawing off my Nesba experience, I all but pretended to cry when I approached the CR afterwards to apologize for stuffing him...he looks at me and says..."Oh I dont give a sh!t, its cool man"
Now..take what you will from that, but I can tell you that if that were Lenny, or any number of other CR's, you'd be getting an earful at the very least. And me personally, I'd prefer that, to at least show me that your looking out for the welfare of the other riders.
Again, the guys at TPM are all extremely nice people, very funny guys and very down to earth, just didnt seem like they were there for the same reasons as the Nesba CR's.