Office 365 Business Premium or E1

Any business under 300 seats it would be worth looking at Business Premium. However, you may find the Enterprise SKUs offer a more flexible product mix. Consider E5,E1 and F1 if your business has frontline workers. I would also workout the business case with the customer to ensure they can see the value proposition of each licensing scenario. Remember your customer is buying a service so these are monthly / annual operating costs as opposed to the on premise purchasing which is more capex in nature. Take your time working through with the customer their needs before starting their Office 365 journey including migration. Good luck!