Even vs Uneven Magnetic Field Cancellation in Toroidal Transformers
Not really... In both cases you use the whole winding (Parallel the connections (watch the phasing, it matters) for the two winding case). 

You sometimes get lucky in a particular orientation, but to a first order the core flux is the same all the way around (it kind of has to be), you are dealing with second order effects here from things like imperfections in the core, but while it is a thing, it is very rare for it to be enough of a factor to matter. 

The big win for lower external fields is using a transformer rated for more voltage (both primary and secondary, and correspondingly more VA), the lower voltage will lower the operating flux and move further from saturation. For the same reason a 50Hz part is usually better then a 60Hz one (even on 60Hz). Aggressively cost optimised transformers often run on the ragged edge of saturation, especially if your mains line is a bit high. 

I get the feeling you may be trying to solve the wrong problem here, what are you actually trying to do, and why does the (really not very large) leakage from a properly sized power transformer cause you so much of a problem?