I'm looking at the V&H Monster Rounds and Oversized 450 Slip ons - one of these sets will be installed in conjunction with the Power Duals Headpipes on a '14 SGS.

I'm wondering, what is the difference between the two, other than an additional 1/2" in diameter? Anyone have some first hand knowledge on sound difference or is it just mainly looks?

 

Found these clips on Youtube. Might be helpful in your decision.

 

I unfortunately can not directly answer your question. However there seems to be some confusion in your question and the videos. Vance and hines offers monster rounds which are 4". Then your second video is a hi output pipe which flares from 4" to 4.5". Now vance and Hines is releasing what they are calling a 450 muffler which is the whole muffler body is 4.5". I don't beleive the 450 is even available yet. I really don't know anything about the 450 mifflers but I'm very intrested in them to be honest. I'm currently running Cfr's and love the look of the 4.5" pipes however I know the CFRs aren't doing my bike any favors in the torque department. I'm hoping the 450s will be alittle more dyno friendly.

 

Just got a set of the oversized 450's with the V&H's header. The sound is awesome! I unfortunately have nothing to compare them to but, they produce a nice deep sound that's not obnoxious.

 

I have the Monster Rounds and really like the sound a lot. From what I have heard the 450's are deeper and louder than the rounds. The rounds are currently being dynoed by fuel moto on their 2015 RG along with a few other mufflers and they perform pretty well. I would guess that the 450's would also do pretty good.

 

I have a 2015 Street Glide with a stage 4 kit installed. It produced 111 hp/111 ft lbs of torque at 4000 rpm. They do produce a very deep rumble.

 

I saw in a previous post you have the V&H 450's but which head pipes are you running with them??

 

i had V&H Ovals and just swapped for the 4.5 Hi Output Monster rounds.The comparison of the two with my Power Duals is ....The 4.5 Monster Rounds produce a deep rumble and are not that loud on my 107 build. Highway its way more quite .. more like a purring... hope cagers hear me.... Bike seems to idle smoother with the 4.5's with same PV Map. no popping... The V&N Ovals are much louder and higher pitch but sound awesome... Noise law here now with db meters, i had no choice.. lets see if LEO's bug me with the Monster rounds this season. Another thing i noticed.. even with Power duals, i thought temp of both sides of slip ons would be equal, but seems once side is hotter than the other... wouldn't the crossover on the Power Duals produce equal temp on both sides?

 

I'd like to take a shot at explaining this: if the pipe ducking under the frame isn't the same diameter as the pipe leading to the slip-on on the right side, it would cause an increase in pressure, as would any bends leading to your left side slip-on. The flow would take the path of least resistance which would be the straight out path on the right side. The x-over pipe doesn't direct the flow of exhaust on the back side of the x- it's open to both. To test this, start your bike up and cover the slip-on on the right and note that all the exhaust goes out the other side.

 

But......... The left side on the power Duals running the HO Monster Rounds is the one that most of the exhaust gases escape from. My FLHX does it and all my friends that run the same exhaust do it !