For even a little bit complex reasoning question, u should use GPT4.
If using code, u can differ it using nlp library such as spacy or bert, they can recognize basic semantic.
Or in advance u can use llm’s function cal to differ semantic.
It’s not recommended to differ directly by python’s if else code with no semantic ability.
In addition, web chatgpt has the ability to switch models automatically, but it’s not in control by us!