Keep your AM set, if only for backup.
Does FM really buy you any necessary capability in CB? Around here you’re hard pressed to find any local activity on AM. I think manufacturers are pushing it mainly to sell new radios.
But my President McKinley does SSB, which is a big step up in capability, particularly when conditions permit skip communications. Skip is dependent on solar activity, which has been at the low end of the 11 year solar cycle for a few years, but is coming back in fits and starts. I’ve been picking up skip AM signals from Mexico and Canada lately, but it’s a crap shoot – some days CB is empty.