No real practical difference on the listener’s end. When composing and conducting music it’s a bit different in that you can divide 6/8 into 2/2 (two sets of three eighth notes)
3/4 groups the eighth notes in twos giving 3 strong beats in a measure on the quarter note beats and 6/8 groups the eighth notes in threes, giving 2 strong beats in a measure on the dotted quarters.
