What is more important - Single LLM based AI Assistant, or a Multi-model one? [I will not promote]

It is quiet evident that a company that trains it own AI model will only use their models in the AI Chatbots (like Chatgpt, Claude, Deepseek, Google Gemini, Grok etc), and a company that does not have their LLM may end up going for a multi-model approach (like Perplexity, Microsoft Copilot, OpenCraft AI). Assuming that all are well built in terms of features (of-course they are not), but lets assume that they are from an application standpoint, what do you think would you prefer to go with?