Pro films are the same film as consumer films & batch, however they has been age/ripen to have the best/consistent colour saturation/toe. Therefore pro films has to be refrigerates to keep its consistency.
Slide films (colour reversal film) are generally use for stock photography because it is easier to make separation from it, also the resolution & color saturation is higher than regular print films. But, the grain of slide films are slightly larger than print films.
My preferences are:
Fujichrome Velvia 50 iso ? My favorite for most out door shooting situation because it have the highest punch for colour saturation out of all films, and deliver beautiful greens.
Agfachrome RSX II 50 iso ? Deliver amazing & the most accurate violet & purple colours.
Fujichrome 50 iso ? Have very accurate natural tones of all slide films, however it saturation scale isn?t as high as modern slide films.
Kodachrome 25 & 64 ? Deliver awesome red colours.
Fujichrome Velvia 100 or Provia 100 ? Provia is the modern replacement of Velvia because it is more tolerant to storage & heat, however it is a bit less in saturation.
Fujichrome Sensia 100 ? Amature version of Provia.
I use to shoot with a full range of 6-12 different films in my fridge, and 6-8 types in my bag.
I now normally carry 4 rolls of Delta 100 B&W, 1-2 rolls of Velvia 50, 1 roll of Agfachrome 50, 1-2 rolls of Sensia or Provia 100, and 2-4 rolls of Reala 100 or Superia 200, when go on shoot around town or a couples of hours drive between home & location. On vacation I now shoot exclusively Sensia and Superia because it doesn?t need refrigeration.
As for the photo contest: Try shooting as much as you can with various type of films & find one that you like that fit your shooting style.
For best result, try shooting with a 50mm standard lens (usually are the sharpest lens in all lens groups) at f5.6~11, and a tripod ++ cable release or remote.