I prefer narrow entries with an "event ID" attached; you can trivially filter to get all of your items with the same event ID, but it works better with all the tools designed for narrow entries.

So instead of one entry with e.g. 27 elements, you have maybe a dozen entries, all with the same event id and 2-4 elements (including the event ID) each. This also lets you log incrementally; if your server crashes before you log the wide entry you have zero data.

It also lets you adjust the granularity. E.g. for a web service you might have both a session and a request ID.