Need to 'sell' meteor to a client. Suggestions please

I have a potential client lined up who is looking to outsource development of simple business management applications.

They requested a walk through of the technology I use (Meteor of course) to see if it’s as ‘flexible and cost effective’ as their current development solution - filemaker.

I’ve seen their previous apps. Horrible UI. Security holes everywhere. A completely unstructured DB that ‘grew organically’ over the last decade.

What meteor features would you choose to demonstrate the power of full stack JS and Meteor?