There are two choices to be made here. No-one can say for sure which shape is the more popular of the two. It can be guessed that local or regional markets would need to be sized up. Speaking of which, no matter where you are in the fashion world today, your belt buckles for men, square (or rectangular) or round can be shipped direct to any wardrobe in the world today.
The round shaped buckle is popular among the cowboys and the outdoorsy types of guys. There is nothing feminine about having an oval shaped buckle around the well muscled waist. But if the midriff just happens to be a case of the middle aged spread, then the bigger the buckle, the better, because it certainly hides what’s underneath that blanket shirt of yours, away from curious eyes.
The square shaped buckle remains popular among all men and it is usually applied to formal wear across the board. But if you’re going to be among the most stylish of dressers then a safe bet is to tone down the buckle to its widely used rectangular shape. But again, the bigger the spread, the more powerful a statement can be made with a thickset square jutted square buckle. It must be heavy metal to be formidable as well.
Why not have two sets of buckles then? One for your everyday formal wear and one that brings out the best in your favorite pair of weekend wear faded jeans. The more faded, the better, because that big buckle shine has just got to come through like the sun at first light. And that’s another thing; look after your buckles, please. Shine them good and proper with a specially formulated polish just for this purpose.