Optimizing for returns
For a fact both of these strategies will work for you in one way or the other. But when you are thinking in terms of the ROI, there might be slight differences from time to time. Over time there are a lot of people who have questioned the ability of Google AdWords to deliver on the promises that you might have heard from someone before you eventually decided to walk that line. Indeed AdWords work but there is so much that you will have to do. Nothing comes easy and this is also the case with SEO. You would really have to do a lot of work in as far as optimizing your website is concerned and it is because of this therefore that you have to at least consider getting either of these services for your website.
Of course one of the biggest differences that you will come to appreciate about the use of AdWords is that you must spend a lot of time and money on them in order for you to learn how to work your way around. You might not need to spend so much in monetary terms when it comes to SEO, but you will still need to invest a lot of time in it for you to get some really good results in the long run. The ROI on AdWords is measurable, and this is one of those things that a lot of people do appreciate about AdWords as compared to SEO.
Monitoring ROI returns
You can use AdWords in such a way that you can monitor the results for your efforts invested as compared to your returns in the long run. This scalability is one of the main reasons why there are a lot of people who often end up going the AdWords way as compared to SEO. Indeed you can still find a way of measuring the returns on SEO, but the main challenge is that in most cases SEO has qualitative results as compared to the quantitative nature of AdWords. Therefore in the long run it becomes a matter of quality versus quantity.
By the end of the day it is all about what works for you, or what you do believe will work for you in the long run. Both of these methods work, but the best thing for you would be to incorporate all of them.