It is always a good thing to get as much tied down in writing as possible when dealing with unknowns, it helps to keep from having misunderstandings, and helps to protect both parties.

People have a way of "forgetting" the details over time.

If you know them, and trust them, and want to deal on a handshake thats different.

There is no accounting for taste.

Experience is a great thing as long as one survives it.

Generally, there ain't a lot that separates the two however,
Barely making it is a whole lot more satisfying than barely not making it.