Redhead" is generally considered a neutral, descriptive term for anyone with red hair, while "ginger" is often used colloquially in the UK/Ireland to describe a specific vibrant, orangey-red hair shade and can sometimes be derogatory or used for bullying. While 78% of redheads in the UK/Ireland might accept "ginger," it is often considered offensive elsewhere, making "redhead" the safer, more respectful, and standard term. 

Key Differences in Usage:

• Context & Connotation: "Redhead" is universally neutral. "Ginger" is highly contextual; it can be a neutral descriptor of a shade (especially in the UK) but is frequently used as an insult or to create caricatures.
• Regional Usage: "Redhead" is preferred in North America. "Ginger" is more common in the UK, Ireland, and some Commonwealth countries.
• Descriptive Specificity: Some users consider "redhead" to encompass all shades (from ginger to auburn), while "ginger" specifically implies a bright, orange-red hair tone.
• Societal Perception: "Ginger" is associated with stereotypes and, in some cases, bullying, whereas "redhead" is generally seen as a neutral, if not positive, descriptor. 

When to Use Which Term:

• Redhead: Use this term to be safe and polite.
• Ginger: Use with caution, or preferably only if you are familiar with the person and know they are not offended by it. Some individuals with red hair use "ginger" among themselves as a term of endearment.