If I've only got one or two buttonholes to make, I just use the automatic one on my newish Brother.
But the buttonholer attachments make gorgeous, hand-made looking buttonholes, so I have to do a whole shirt, then I'll go to the little bit of extra trouble of setting it up, testing it and marking the fabric, etc.
I usually go around each buttonhole twice - I think that's what gives them the look of hand-stitched with buttonhole twist.