Since deferred adjudication in Texas requires the defendant to enter a plea of guilty or no contest, there is a felony conviction.
This might vary state to state.
I know in some states a criminal DA (as opposed to a speeding ticket DA), does not result in a felony conviction. It is exactly what it is sounds, disposition is deferred and the case is still open. During that time, your indictment is still open so you cannot buy a firearm. But once the disposition is final and charges dropped, there is no criminal conviction record and no relief is required.
Of course now relief is required, as there is a record it is a DA and laws are now being put in place to treat a DA like a conviction. Sounds racist to me.