i think one should found florence when playing with italy. reasoning is that with italy's UP combined with city states, your cities will have much more food than you could supply happiness for them. you could get venice, rome, and florence above population 16 at around 1500 AD. and much more than that by 1600 AD.
with italy, there is not much point in trying to get cities with as many tiles as possible because
1) city states allows only 7 land tiles and
2)why work tiles when you should be working specialists
3)italian cities can get very big, the only problem is happiness
so, with my logic, why have Rome and Venice at size 16 when you can have Rome, venice, and florence all at size 16? even if you dont allow Florences's working tiles to be anywhere in the sphere of venice and rome, florence would still be a huge city.
having Rome as capitol might be better though, not because it is a better location than florance, but simply because you will suffer slightly less distance maintanance costs for the cities you capture/settle in africa.