It still surprises me how much bile these two get. I always thought they were pretty funny and entertaining. Maybe people just found them too over-the-top and goofy? Which even I will agree that it is unfortunate that we never had another antagonist in the series quite as good as the original Sharptooth. Still, I think Dil & Ichy were two of the better villains for sure.
I will admit, it also surprises me how most people seem to prefer Ozzy & Strut, whereas for me it was the opposite. More surprising still because I always had the impression that LBT 4 is the most popular of the Roy Allen Smith sequels, and one of the more popular sequels in general, although I guess it's for reasons other than Dil & Ichy.
Perhaps the reason I didn't care for Ozzy and Strut was because I found them too jarring a contrast, coming on the heels of the menacing Sharptooth from the first movie. Whereas by the time I made it to the fourth movie, I was more used to the idea of comedic villains. Although I still think Ichy and Dil were more well-done in that regard anyway.
Beyond that, though, I'm not really sure why I liked Dil & Ichy better. It's hard to articulate.
They both speak the leaf-eater language in the film, which is curious, especially in the case of Dil who is an obligate carnivore. How do you think that Dil learned the language? Was, as proposed in this topic, Dil and Ichy formerly friendly sharpteeth? Or do you have another idea that you would propose?
A good question, albeit one that I never thought of before. Note that Ozzy & Strut can speak it too. Hmmm. The best answer I can offer is perhaps that regular T-rex Sharpteeth have their own language, but most of the other dinosaur species all speak the same common language, which includes Dil & Ichy. Even though I guess Dil could count as a Sharptooth as well, she seems different from the standard Sharpteeth due to being a crocodile. Or else perhaps she learned to speak it from Ichy, although I'm learning more towards the former explanation.
However, that itself leads to the question... why do T-rexes have their own separate language from everyone else?

Regardless, I do think the language thing is an interesting concept, and one that I wish the series had explored further.