pick sufficient pot size for length of vege you agreed upon for contest. Bigger may only bring problems and few benefits if it has no time to get large enough to make use of it.
if sativa structure (limited axillary growth), i think LST does a better job bushing those out, initially, than topping (top later to control level of canopy, spread it out mroe).
if indica... Think topping is a bit faster overall - at least to start. certainly more easily organized when topping to fill a space. If you got time, top then lst until branches are where they need to be to grow vertically. i.e. get X primary branches (from topping) trained out horizontally over area before allowing to grow vertically... top where needed, lst otherwise etc etc.
LST/topping often requires removing some growth in congested areas.. .any growth you remove is just wasted effort for the plant that could have grown something else that would augment yield. So, if you cna visualize one path requiring less waste, definitely the way to go.
i'd get real specific about how i organize it too... even it out vascular tissue however it calculates to fill the space -- i.e. any primary branch off apical meristem will support same number of colas. Having the vascular tissue as evenly split as possible between all colas will help avoid larf, which i would think should increase yield.
