Structured Logging (JSON Logs in Python and PHP)

What's the primary advantage of JSON structured logs over free-text logs in production?

• AJSON is smaller on disk
• BLogs become queryable by named fields, so questions like 'count 5xx by URL' become single filter expressions instead of regex hunts
• CJSON parses faster than plain text in every language
• DIt avoids the need for log levels