My bars are modeled on the first Vendetta for two reasons:
1.) The most important reason is comfort... for whatever reason, for me, holding the hoods with the arms straight feels awesome.
I experimented for months, off and on, to settle on what works for me.
2.) Like the Great and Good Ratz says, aero is king and straight arms will give you second-best aerodynamics on the Vendetta.
The best aerodynamic position for your arms is tucking them out of the slipstream altogether, like Larry does on his custom hamster bars.
Other reasons are, in no particular order, are:
A.) The hoods are another place to rest your hands;
B.) The hoods are where you control your brakes and gears, so holding the hoods is kind of a good idea anyway;
C.) I dunno about Ratz's idea that you need your biceps to muscle extra power into the Vendetta... if it works for you, more biceps to ya.
With my arms straight, I can use both my triceps and biceps but I primarily use both my shoulders and core to pump more power into the bike.
The design of the stock seat back frees up your shoulders;
D.) John Tolhurst designed a bullhorn bar for the Vendetta and this is what I was aiming for.
However, instead of using bar-end shifters and TT brake levers, I use brifters.
If your bars, hoods, levers and whatevers are working for you, fine!
Don't worry, be happy.