Difference between 更好 and 比较好?
Here's my take on it.

更好 = "even better." For example, X很好。Y更好。= "X is good. Y is even better." This comparison could be over time too: X已经很好，现在更好了 = "X was already good, now it's even better."

比较好 = "better", without an implication that the object of comparison was/is already good. So, it's acceptable to say X不怎么样，Y比较好。= "X kind of sucks, Y is better"

For more example sentences, check out Allset's grammar wiki: 更 geng and 比较 bijiao.