Of course Wonder Rubber is much harder to trim; it takes longer and requires more patience, than softer rubber.
But I'm scratching my head trying to figure out your sequence of events.
In your OP, you bought donuts and had a problem: "mounting and putting on and off different cars I don't know which is what?"
Then 2 days later, you "trimmed both on my Hudy" and deduced "the Super Nats were easier to reduce in size".
1. I mounted 2 pair of each and one pair each were trimmed to the same size for testing the others went back in the Eagle Dist. bags and into large tubes.
2 Played with trimmed tires on various cars and a week later I didn't know which one was which when I went back to the track.
3 When I went to compare the trimmed to the untrimmed I noticed that the wonder donut bag was priced $2.50 a pair and the Super Nats were listed $4.36. i.e. backwards.
4 I posted on Slotblog asking for help (See post 1)
5 I used the information from Slotblog to figure out which is what.
6. Trimmed the second pair of each tire type today.
7 I posted on Slotblog (See post 11)
8 You got confused (and the thought of a confused Pablo made me sad)
9 I posted on Slotblog (See this post)
10 Hopefully Pablo will no longer be confused and I can be happy again
Mark