Advantage: Purist would argue that its not necessary, dam ugly and if you swap out the current exhaust you can gain 2-3 h.p and more authenthic sounding machine of that era. Strictly a matter of preference nothing wrong with keeping it stealthy either.
Disadvantage: Probably have to rejet carb/change needle position, cost of replacement exhaust and time spent checking spark plug color and effects of carb rejetting...also readjustment of air/fuel ratio.
The above is factors concerning iron...Believe Thunper AVL procedures are taking into acount his AMAL carb that he installed but the premise is the same. I've kept my 28 mm Micarb and all of the above took me approx 4 hours as it's been a long time since I done it....Throw in a Snidal book for a good explanation of both the Iron/AVL transformation..
Apparently the PAV location for the AVL on top of the exhaust valve vice where mine was at the top of the exhaust pipe...I see that CMW does sell different exhaust for the AVL . AM I to assume that the AVL PAV can stay in place and you don't have to remove it..Just replace the OEM exhaust?
A blanking plug is mentioned but that can be used also for the Iron users who want to keep their existing OEM pipe and just remove their PAV connection..Some of these users have done so and remove some of their baffling inside the bazooka style OEM exhaust...Guess its a cheaper way to go for effects but I've found that the internal design of that exhaust isn't just take a long drill bit and run it thru as both ends have turns in them before entering the baffle chamber...
Bottom line: If the OEM enhaust fits your expectation, stay with it..If u want to experiment without any serious effect on the bike, go at it...Their is a noticeable difference in H.P.....cheers.