The Truth About Different Types of Cubes:
Most cubes look alike.
All cubes grow in the same conditions.
The differences between cube races, varieties or 'Strains' are, more often than not, minute.
Some races are known for fast colonization, or large fruits... even high potency.
BUT... these 'Facts' are often just vendor hype.
Your results will most likely vary.
The Truth About Cube Potency:
If you want something that is very potent, you should probably try a different species and avoid cubes all together... either that, or eat more cubes. Agar will potentially allow you to select a more potent substrain. A few cube races and varieties are reported as being more potent than others... but there is no scientific evidence to strengthen the potency argument. Everybody wants the answer to this question... but all we have is opinion. Most people agree there are differences in potency from one type of cubensis to another... but they seldom agree on which cube is the most (or least) potent.
The Truth About The Fastest Growing Cubes:
Some cube races and varieties are known to grow at a faster or slower rate, on average, than others. There is evidence which suggests the fastest cubensis races produce the smallest shrooms and the slower races and varieties produce the most bulky fungus. Ultimately it all seems to even out in the end (with a few exceptions). Also, the slow cubes more frequently display unique macroscopic characteristics (in other words, they are more likely to look noticeably different from other races) while the fast ones usually look like average (or smaller than average) cubes. It tends to take more time to grow a large or unique cube. If you are looking for a cube which produces a LOT of quick bulk, you may be looking for a long time... and you'd better work with agar.
The Truth About Bulk:
Race, variety or 'Strain' has little to do with bulk. With some work, any viable cube print should produce good flushes. Good isolation on agar, and good fruiting conditions are the only proven ways to get consistently bulky flushes. There are no quick and easy solutions. If you want bulk, first you are going to need diligent patience.
The Truth About Selecting Your Spores:
The thing that distinguishes most races, varieties or 'strains' is where they originated and who collected the first specimen. If you are interested in Tasmania, try some Tasmanian spores. If you like the story of how SG30 was resurrected by Shdwstr, try SG30. If you think Penis Envy looks fun, try it. They are all cubes. Pick one that interests you, and see if you like working with it.
edit: I copied this. Not my own words