Best Type Of Client

This might be a dumb question but just curious as to what makes a client/company particularly easy to work with? Is there a certain deal-type that typically goes over more smoothly than others? What about a particular size of company? Is it easier to give advice to perhaps a worse-performing company because they’re more likely to listen to advice/make a transaction go through? Or perhaps a larger company since it might be easier to find market research/data on?

Thanks for the insight!