Triangle vs Square vs Pentagon?

I'd say that it is guaranteed that you are able to route payments to any of the participating nodes, at least initially. So, the more nodes, the better. On the other hand, larger swaps may be more likely to break down at some point in time due to the failure of a single channel, and it takes more time to find the needed participants.

There is a similar question here if you're interested: https://lightningnetwork.plus/questions/51

In general larger shapes are beneficial for groups of friends or any group who needs to be connected and you don't want to waste SATs opening multiple triangles. It's also beneficial for new nodes with few connections. A pentagon usually opens the entire network to a node instantly. In any other case do a triangle.