What is the best service to use when requesting data for a specific point? For example we have graphical data that we can expose using any of the services. If we want to build a request url that uses a lat/lon point or even an airport ID, which service would be optimal? We want to provide known points within the request.
If query by airport ID is a requirement then WFS is the only solution. WMS and WCS does not support queries by attributes. WMS GetFeatureInfo supports only query by a point and even then some tweaking would be needed for making it to work with lat/lon coordinates. WCS is all wrong service for your needs because it can only deliver coverages (usually raster data) but not information about features.
I would go with WFS with PropertyIsEqualTo of PropertyIsLike filters for attributes and DWithin filter for searching features nearby.