Speaking of spawn intensity, how much better would a 90% be versus a 60% of the same beast, same spec that was fully trained?
that is totally dependent on the animal and their spawn intensity range.
From worst possible to best, a hiryu has a 932 intensity range.
Taking a
18% Hiryu and compare it with a
80% Hiryu (click on links to see the planners for each)
The 80% gets substantially more hit points, stam regen and mana.
In some animals a high intensity can be the difference of having certain specs and abilities, especially if the pet is considered "tight on points" due to innate abilities.. Again, it all depends on the animal.
Now as for a 90% to a 60%, a 90% spawn is most likely impossible on most animals except those that can saw as 2 possible control slots (lesser hiryu, reptalons, nightmares, naja, etc) On animals that always spawn in the same control slot range, again it depends on an animal, but i would shoot for a 65-75 range. Even 80% on a lot of animals would be
extremely rare. Unless of course you are a minmaxer to farm for a 76+, a 65-75 will most likely work for your needs.