They are both excellent products. In terms if a White Balance, both will give identical results, as both are truly neutral. The Passport has the advantage of allowing you to make Lightroom Camera Profiles, and has warming patches, but at a $100 price point. It is somewhat bigger than our studio version, and while well made and packaged, it is somewhat of a pain to use in the field because of its size and that you need to open and close their case to use it.
The WhiBal has the advantage of Price, small size, and faster operation. So if all you need is accurate White Balance there is no advantage to the Passport. If you will use the additional features of the Passport you have to weigh its much higher price.
i find the most useful use of colorchecker passport/classic/mini to correct color via profiles.
for white balance, colorchecker grayscale patches its not as neutral as whibal, and test showed too much variation between colorcheckers for my taste. also, spectral response its not linear as whibal. and yes, aim a "precision-holic" ;)
also, whibal its more practical for everyday use. once you done the color profiles with colorchecker on the environments/lights you use, you don't need to use everyday, only in "light-challenging" situations.
also, the effect of warming patches can be done just adding +200k in temperature and +7 in tint (in steps) in adobe camera raw, so, there's no "magic" in warming patches.
i have a mini-colorchecker and im waiting for my whibal to arrive. both are must-have tools in my opinion. ;)