Though lilac and lavender are somewhat similar in color, there are huge differences, outside of the fact that they are both perennial flowers. Lilac and lavender are both purplish-blue plants, however lilac has a flower with more distinct petals and lavender flowers are much smaller. It is perhaps for this reason that lavender plants are more adapted to tolerating high heat and low water conditions than the lilac plant. However the smell, more than any other characteristic difference, is the most important difference between lilac and lavender.
If ever you are purchasing body care products that are purple in color, such as soap or body wash, it is most likely lavender scented. Lilac, although there are obvious exceptions, does not produce the same type or strength of smell. Therefore, it is rarely used to produce items that require a strong, sweet aroma. Lavender's extracted oils are also particularly useful, especially when it comes to aromatherapy and massage oils.
Lavender is by far the more useful plant and is considered one of the most precious of all herbs. There are numerous things lavender extract can be used for, such as fragrances, makeup, cooking, healing, and housekeeping. Lilac is not nearly as versatile, although its flowers do provide a delicious smell.
Both flowers will undoubtedly add to the beauty of your garden, but where lilac lacks in the sensory department compared to lavender, it more than makes up for it in the visual department. Compared to lavender, lilac plants have a much fuller appearance. Lavender slightly resembles long grass with purple blooms decorating its tops. It has its own unique beauty, but gardeners who aren't looking to harvest lavender and use it as an herb may prefer lilac in their gardens. Their bushels of pastel colored flowers are sure to be a hit.