LlamaIndex vs LangChain

import { VectorStoreIndex, SimpleDirectoryReader } from 'llamaindex';

const documents = await new SimpleDirectoryReader().loadData({ directoryPath: './data' });
const index = await VectorStoreIndex.fromDocuments(documents);
const queryEngine = index.asQueryEngine();
const response = await queryEngine.query({ query: 'What is the main topic?' });
console.log(response.toString());

from langchain_openai import ChatOpenAI
from langchain_core.prompts import ChatPromptTemplate

llm = ChatOpenAI(model="gpt-4o")

prompt = ChatPromptTemplate.from_messages([
    ("system", "You are a helpful assistant."),
    ("user", "{input}"),
])

chain = prompt | llm
response = chain.invoke({"input": "Hello!"})
print(response.content)