I'd like to get an idea which Monster Oval slip-ons you like better. But we are just going to compare the regular Monster Oval (16755) to the Twin Slash Monster Oval (16765).
That's not what Vance and Hines told me. They said they are exactly the same except for the end piece. Same sound, same loudness, and same performance.
Personally, I think the twin slash look better, but they may be an issue to clean (more sharp edges). I had the regular MO's on my Ultra, and I loved them, but the tips did collect a lof of carbon from the exhaust, I think the twin slash might hide some of that.