Wait a week (or so) and evaluate Grok 4.
They are all very similar at this point (the top models). Claude is the best for coding, some are better for visual stuff, but for pure text stuff you won't see a huge difference so you can be driven by price.
The Grok team iterate faster. OpenAI are the 'leaders' right now, but with the exodus of talent and these huge data centers their competitors are setting up I'm not sure how long that will last.
I'd recommend picking a monthly plan over a yearly one so you can swap as you need to.