Test prop has an ester attached this is why it is test prop, because it has a propionate ester on it that increases the half life of the drug to 1-2 days and the size of the molecule. Test base (also Tne test no ester) has a much shorter half life 12hrs or so and is a smaller molecule. The smaller molecule is much easier to use in a transdermal setting because it goes through the skin much more efficiently. For injecting most prefer the prop because they can inject EOD and it is generally less painful that Tne suspension in water.
Test prop in oil http://www.bodybuilding.com/fun/cattestp.htm
Test suspension (test no ester, test base) in water http://www.bodybuilding.com/fun/cattests.htm