I noticed that the summer dinner jackets on offer by one of this country's larger retailers have peaked lapels this year, and thought I had better remind those few men contemplating the purchase of a new jacket that if one is going to wear the white it is best when shawl lapelled.
Peak lapels you see are descended from white tie and are the more formal style for evening. Shawl lapels are descended from the less formal smoking jacket, though that is less important than the fact that the style looks considerably more graceful with a soft turndown collar shirt than does the peak.
Now there are those that argue that the white dinner jacket should only be seen on cruises, if then, but I find it easier to wear these summer days than its darker counterpart. Without the black jacket's silk facings on its lapels it attracts less undesireable attention in venues where the typical dress is considerably less formal, such as any casino in Las Vegas. Pit bosses, on the other hand, definitely notice.
Accept no substitutes.