Contact cements are ready to go in minutes: E6000 requires days to cure, cleans up with lacquer thinner. I have used both and each has advantages, disadvantages for any given purpose. I would use contact cement where alignment is easy but the E6000 is better if, for example, one is blind-attaching a piece down inside of a boot where applying cement to both surfaces and aligning attachment is impossible.
The slower cure of E6000 can be effective where additional adjustment, dry-shaping and clamping occur immediately after gluing.