Their CPU benchmarks indicates better performance for the C4 compared to the RPI4 though. Is it due to the A55 being more recent ?
For benchmarks that depend only on the CPU, using an improved cooler on RPI4 would increase the sustained performance above Cortex-A55, except for some custom programs that could be written to take advantage of the newer extra instructions available on Cortex-A55.
A quadruple smartphone core like the obsolete Cortex-A72 or any of its successors, Cortex-A75, Cortex-A76 and Cortex-A77, requires a smartphone-sized board, unless you use a noisy fan for cooling.
There exists also the fanless ODROID-N2, with a quadruple Cortex-A73, which, being well designed, has a larger board, which has an area similar to a smartphone or NUC.
The RPI4 has a too large CPU for its size, unless fan noise is considered acceptable.