I would have to say a roller. Also i think a roller looks more professional instead of have chains hanging down. Most mowers will leave a nice strip without using a stripping kit, if you know how to use it.
Buy the roller. I made a stripe kit from convair belt. It work as good as the roller. I have it on 3 mowers. I also have jungle jim wheels on the 2 walkers and the blades i use make the stripe even better. NOT all mowers make a stripe you can see. But you can make mowers make stripes that will make everyone look. Jim