Well there is no way to say which strain has the most crystals, while some strains definitely have more resin production than others I believe it is also highly variable upon growing conditions including indoor/outdoor. I would say that indoor will probably have a more frosty look in the end product because it isn't subject to the harsher outdoor environment. There are some strains that are used more frequently for the process of hash making, Hash plant being the most obvious. Out of newer generation strains I would say that Alien OG is the most trichome covered I have seen in a while. Here's a picture of it.
Alien OG is a cross between Alien Technology and OG Kush. It has a good Lemony OG scent and taste and it is absolutely covered in trichomes. The Alien Technology plant is said to have been found by a soldier in Afghanistan and it is noted for its unearthly resin production that gives these buds a beatiful snow covered appearance.