they are different in the aspect of the time that it takes to release the active hormone (testosterone) and the vehicle in which the test is carried (oil v. water). that being said, test suspension works almost immediately and has a half-life of about 8 hrs. it has a real kick to it and can be good to take right before a meet, or even in a cycle, the only drawback is daily or 2x daily injects. most oil based test is esterfied (some ug labs produce test suspension in oil), meaning that it takes a longer time to release, and the release time is based on the ester of the testosterone being used: half lifes range from 2 days (acetate) to 24 days (laurate). all test is chemically the same regardless of the ester, so one type of test is not necessarily better than another. what YOU personally use should be tapered to your goals