The honest ranking for our conditions, toughest first:
Ganache leads - it's chocolate-based, so it handles heat better than any light cream and firms up beautifully. For summer orders and long deliveries it's the safest beautiful option.
Italian meringue buttercream is the most stable of the meringue systems - the 118°C cooked syrup effectively pasteurises and strengthens the foam - with Swiss close behind. These survive a delivery run that would murder the softer creams.
American/simple French-style buttercreams sit lower: lovely in winter, fast-softening in summer. If you use them in the hot months, work in AC, and the finished cake goes into the fridge immediately and travels cold.
Whipped cream is the fragile one - it was never built for a Delhi afternoon. Fridge-to-hand-delivery only, shortest possible window.
The real skill is matching frosting to season and route, not finding one that does everything. Ganache summers, buttercream winters is a legitimate business calendar 🙂
