I have a Strida folding bike for commuting in NYC by ferry and subway too. Love it.
Wheel diameter doesn't matter for climbing, though. Bigger wheels are more efficient on a flat surface by way of less rolling resistance; the bigger wheel creates a smoother tangent with the road surface, and contains more air so deforms less under its weight load. But when you're climbing, rolling resistance means almost nothing compared to the energy you need to supply to climb the well of gravitation potential.
The problem with climbing on a folding bike is frame rigidity. The geometry required by most folders (long single tubes connected by joints with necessary slop for folding) means that a fair bit of the energy you supply goes into stressing and flexing the frame rather than transmitting into the drive system. The traditional brazed diamond frame doesn't have that problem. To make an extreme metaphor, climbing on a folder is a bit like pushing a string, where the energy goes into deforming the nonrigid body instead of moving it.
If wheel diameter mattered for climbing, then either skateboards couldn't climb hills or they'd have bigger wheels for doing so.
Wheel diameter doesn't matter for climbing, though. Bigger wheels are more efficient on a flat surface by way of less rolling resistance; the bigger wheel creates a smoother tangent with the road surface, and contains more air so deforms less under its weight load. But when you're climbing, rolling resistance means almost nothing compared to the energy you need to supply to climb the well of gravitation potential.
The problem with climbing on a folding bike is frame rigidity. The geometry required by most folders (long single tubes connected by joints with necessary slop for folding) means that a fair bit of the energy you supply goes into stressing and flexing the frame rather than transmitting into the drive system. The traditional brazed diamond frame doesn't have that problem. To make an extreme metaphor, climbing on a folder is a bit like pushing a string, where the energy goes into deforming the nonrigid body instead of moving it.
If wheel diameter mattered for climbing, then either skateboards couldn't climb hills or they'd have bigger wheels for doing so.