It completely depends on your aims and objectives.
If you are looking for more guaranteed, short-term results, then paid advertising will be better for you. However, just bear in mind that not having your website optimised for SEO means that your offering will disappear once your paid advertising campaigns stop.
Likewise with SEO, it may take longer and more patience to see results.
We recommend, when you are in a position to, doing both in order to be successful with being found via search engines.