There is no specific answer to that question as it depends on the use cases of the customers. 

This question is linked to performance !

Keep in mind that when you have many Point of Sales and you are in real time, each order that you will synchronize to the server will take a bit of time. If you multiply the amount of orders and the amount of Point of Sales, you can quickly get a high amount of time required to perform these synchronizations.

The risk is that you overload the server and your orders are not synchronized.

The same logic applies to inventory adjustments. If you have many operations on the same product in the same location of your inventory, you need to wait until one operation is completed before you can proceed to the next one. As a result, it is also advisable to configure one WH per Point of Sale configuration. 

In some cases, you might need to at least configure 2 different locations (for each POS configuration) if you are in the same WH for the shop.

In the current master (target V16), we select real time by default. The point of having the possibility to switch this configuration at any time is to be able to manage the volume of orders depending on the business need and at different times (normal day vs black friday for instance). 

As a side note: if you are on odoo.sh, note that having more workers doesn’t help in this performance question.