Endocrine system regulation slowly happens but produces long-lasting effects, whereas nervous system regulation quickly takes place with short-term effects.
Endocrine system can regulate many things in the body that control the metabolism. The effect shouldn't be instant, but it should be good for long term effect. Nervous system need a much faster reaction because it responsible for "fight or flight" reaction. A slow nervous system will cause the organism caught by predator easier.
Thymine has a methyl group and is better suited for the storage property of the DNA molecule as it is far more stable compared to Uracil. RNA contain Uracil instead of thymine so as to make differentiation of RNA molecule from DNA molecules easier.
