All things have their place and supplementing one in place of the other when is comes to SEO, SEM / PPC, advertising, branding or lead generation is not always the best idea. So when it comes to online marketing and implementation, which is the best for you and why?
To answer this, finding out where you are at in the game (fledgling, seasoned or just getting warmed up) and what tactics are already in play is the first step. The next step is to understand the sales cycle and the supply and demand of your audience and industry (and where your product or service fits in).
Aside from the obvious, you need to gauge the scope of the reasons why you are implementing each method (SEO, SEM / PPC, Advertising or Lead Generation) and pair those reasons with the best method to get the job done (within a reasonable budget and time line).
Not to take a chip off the old adage of time and money, but in reality, both are key motivators that have inherent bench marks for competition and successful online ventures.
If a solid return on investment (ROI) is your objective (which it should be if it is not yet) then two things you must come to grips with are (1) finding attainable and profitable strategies and (2) being to implement them in a timely fashion (or at least better than your competition) in succession to create a stable income (to use for more marketing and promotion for the next round).