The number of shapes and sizes can drive you crazy!!! Back when I tried to race I loved these really deep Merckxx bars but now today I find I like a much shallower Nitto (and cheaper) bar.
In general I agree with the shoulder width as a starting point for bar size but after that you use what makes you comfortable. I know guys who love Pista (track) bars on their road bikes, and others who would not use anything but a Cenilli Mod 64 even if they were given solid gold bars to use.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk