Primarily looking to test out app concepts and website ideas. What is exactly the main differences or pros\cons with each of these LLM"s when just 'having fun' 'shipping code' ?
None that should matter to you. Maybe you should start with something cheaper instead of SOTA e.g. Deepseek, Mistral, etc. They're not as good but not as bad as some say either. These cheaper LLMs will allow you to experiment much more until you get some sort of workflow on using LLMs and the switch to the expensive ones.