I'm not an expert on Bitcoin's scripting language, but here's a few main takeaways

* Ethereum allows shared state between transactions, Bitcoin doesn't. That means one application can state "The price of Eth is $10USD" and a totally unrelated application can reference that value. The result is that each application provides an API that all other applications can call.

* Both Bitcoin and Ethereum have a stack based scripting language. However Ethereum also has a higher level language that compiles to the stack based language. That means you can right reasonably readable code without OP codes. Functional program is so much mentally easier than writing a stack

* Ethereum (unlike Bitcoin) is Turing complete. It can have code that loops and recurses based on the state of the chain