Large format lenses as an average seem to have better bokeh than 35mm lenses. I think this is due to better quality control from lens to lens, and also to more aperture blades, creating a 'rounder' aperture. A perfectly round hole should have a very smooth diffracion pattern. When you use blades to create the aperture, you get diffration 'spikes' from the angled corners. You get two for every corner, radiating 180 degrees from each other radialy from the lens optical axis. If you have an even number of blades, you will have as many diffration spikes as you have aperture blades. If you have an odd number of blades, you will have twice as many diffration spikes. (even numbered apertures have the 180 degree spike superimposed on the opposite blades spike). You can easily see the spikes on bright points of light in photographs, especially when the lens is stopped way down. Even old LF lenses have many bladed apertures (20 or so), compared to 7 or 8 for your typical 35mm lens.