What about custom entities?
Every business has its nuances, and this is catered for with an option to create customizable entities and fields. Sales Professional does limit this to x15 custom entities, while Sales Enterprise is unlimited.
OTHER CONFIGURATION CONSIDERATIONS
Again here, Sales enterprise has unlimited access, but Sales Professional is limited to five guided process flows, two forms, two views, five system charts and dashboards, and a maximum of fifteen queues.
All Licenses are paid for or canceled monthly, here are the prices:
Sales Professional @ £49.00 per user / month
Sales Enterprise @ £71.60 per user / month
One of the real benefits for Sales Professional is that it can be very quickly deployed using existing Office settings, but your License will be on a named user basis, whereas Sales Enterprise can be Licensed by user or device. Enterprise users also have the advantage of dual usage rights between Dynamics 365 on-premise and cloud.