There is no difference between an "SDE view" (which never really existed, anyway)
and an "SQL view". A view is a view -- It's always been a database object, created
and managed by the database. If there was any difference, it was in the creation
process -- back before databases supported geometry extensions, the 'create_view'
operation had to populate metadata and create extra views to support the F and S
tables. The result was still a SQL view. Modern best practice is to use SQL to create
views (keeping in mind ArcGIS requirements), and register the views afterwards,
but this has been best practice since the 'sdelayer -o register' option was added
back in 8.x days.
- V