PIOs might be heavier on hardware resources

>The BIO uses 14597 cells, while the PIO uses 39087 cells

and BIO might reach higher clock speeds

> when ported to an ASIC flow, the clock rate achieved by the BIO is over 4x that of a PIO implemented in the same process node.

but BIO is ~15x less efficient per clock. RP2350 is capable of reading IOs at 400Mbps (https://github.com/gusmanb/logicanalyzer) and bitbanging at 800 Mbps (HSTX). From Bunnie writeup BIO needs 700MHz to do pedestrian 25Mhz SPI.