Olfactory information gets to the brain very quickly, but so does auditory, tactile, and visual information. The differences would certainly be measured in milliseconds, and it would have no practical consequence. What they don't tell you is that the sight of grandma's photo or hearing her voice can do the same. All the senses are part of a massive network that links all parts of the brain. Smell enjoys no particular advantage when it comes to access to or speed of access to various parts of the brain.
Natural oils are better than synthetic ones.
It is possible to make a synthetic preparation identical on a molecular level to the most important compound in an essential oil. Given that essential oils contain several compounds, it seems possible that a natural oil might have more than one active agent. If that is so, then aromatherapists should be spearheading the research effort to determine which chemical compounds are inducing the changes they claim are taking place. Instead, most of them seem all too willing to assume that natural oils are better, and that there is no need to defend this assertion with any rationale or research evidence. Essential oils can help your memory.