Other way around: It's the V10s that were far more balanced. Neither design is naturally balanced, but 90deg and 72deg engines can be balanced with a split crankshaft. In the V8s, they're restricted to 90degs, and while the design itself is more balanced, the secondary vibrations made things far more complicated than they were in the V10s.
I respectfully disagree. The V10 engine design is NOT an inherently balanced design, whether its a 90 degree or 72 degree V-angle. I understand that the F1 engines required a split crankshaft, and that proves my point.
V8s aren't perfectly balanced, but the only part that makes a 90 degree V8 unbalanced, is the 1st order free moment (Bosch Automotive Handbook, 7th Edition, pg. 475). V10s are far more complicated to balance, and I5 engines are similarly odd.
If you want a naturally balanced piston/cylinder engine design, go with any of the following:
1. Flat 6 (Porsche 911)
2. Inline 6 (E46 BMW M3, '54 Mercedes-Benz 300SL)
3. V-12, 60 degree V-angle
4. I think Flat-12 engines are also naturally balanced, but I'm not 100% sure. (Porsche 917K)
And contrary to popular belief, Flat-4 engines are NOT naturally balanced either! (Free moment of 2nd order)
But the Flat 4 in my '64 Porsche is damn smooth at 100 MPH.
I would love to see F1 adopt a new Flat 12 engine design. That would be wicked. Displacement around 3 liters sounds about right. I'm looking forward to this coming August, when the Porsche 917s will be out on Laguna Seca. They sound fantastic!