Question Fly SFO to Heathrow then Train to Manchester or Direct to MAN?

I'm planning a trip from SFO to Manchester, UK, and noticed there are no direct flights. I'm considering two options: flying into Heathrow and then taking the train to Manchester, or booking a flight with a layover that lands directly in Manchester (MAN). Has anyone done this route before? I'm curious about the pros and cons of each option, especially regarding time, cost, and convenience. Also, if you've taken the train from Heathrow to Manchester, how was the experience? Any tips or advice would be greatly appreciated!