People have ported FreeRTOS have ported it PSoC5. I am not sure if anybody has done it for PSoC3. These threads might help,
Does the PSoC5 run much faster than PSoC3? their max clock are both 67MHz.
PSoC3 core is a 8051 processor with a, well, it's widely used but a bit out-of-date architecture. The instruction-set shows a couple of different addressing-modes, but the more complicated they are, the more CPU-cycles it takes to perform them. Working-registers are few, but there is a fast mechanism to switch context in cas of an interrupt.
Arm is a state-of-the-art 3-address CPU with more than a handfull of registers. As a RISC-machine (Reduced Instruction-Set CPU) Instructions are executed in a very few cycles.
So, running at the same clock-rate the ARM is running inherently faster than the 8051. To measure the advantage from PSoC 3 to PSoC 5 you would have to use a benchmark program, that Cypress sure will have.