Do the arithmetic on both before choosing. Email: no cap, you control volume, reply rates on a well-targeted 400 person list are single digit percent, and the list is exhaustible. The other: hard cap around 100 invites a week, but a connection is a durable asset - you post and they see it for years.
They're different shapes. If your buyer lives in that feed, the cap is annoying and the compounding is real. If your buyer is a lab manager or a plumber, you're fishing in the wrong pond entirely.