I think side is more elegant and practical. Â I think center if done right is great too, but it will never be as elegant or as practical as side venting.
Practical, I agree. I just bought a long topcoat with a center vent, and it demands quite a few contorsions when sitting down in my car to make it comfortable and to prevent wrinkles. Elegant, though, not necessarily: have you ever walked behind a man wearing a blazer with side vents? Up and down, up and down, goes the piece of fabric against the lower back... It is a different matter with a topcoat, but the flow of the fabric as I walk in my new topcoat is something I find quite elegant.