someone summed it up nicely on the iracing forums, with the OTM it was hard to get anywhere close to the limit on the ovals, now with the NTM it's a lot easier to get to about 90% of the limit before getting progresively harder to extract the last few % which is far closer to real life.
i'm looking forward to trying it on a proper road car though, especially since the current example of the NTM is designed to mimic the real life NASCAR tyres property of being very grippy when cold and rapidly loosing some grip as they warm up over 1 lap (i assume in real life a lot of this is due to the need for the cars to be safe going straight onto an oval from cold ) but so far it's very impressive, the weaving steering business is strange though, i've got a very slight vibration but none of the shaking some people are complaining of.