Those that know how to create an Amazon sales hub that makes sales will tell you that Amazon is the better revenue earner.
Those that do not know will tell you that adsense is the better option.
If you have low visitor numbers then adsense will take a long time to produce any significant income.
For Amazon you can have low visitor numbers but still make a reasonable return on effort.
It takes a lot more time and effort to create good adsense targeted articles - and you are never guaranteed any external viewers,
Once you have mastered the Amazon hub then they can take around 2 hours to create. If, over time, you earn $20 then that is a good return on effort.
I recently created an Amazon hub that generated $230 of sales in the first day (2 sales) which netted me $8.60 at 4%. Since I have got to 6% so far this month that has increased to $12.90 for about 2 hours work. And it has generated some adsense revenue. And it is there for posterity to generate residual income.
I am not an Amazon expert but I can see the potential.
I started off being a writer of hubs for adsense but I am now a convert to Amazon.
Amazon is the way if you want to undertake this game professionally.
One clue that has made a difference to me with Amazon is that you should offer products that are not readily available in stores. Maybe not as critical when city dwellers visit but invaluable for those visitors that live in smaller towns and out in the country, where they cannot get the more specialist products (or even common products, but with limited options / alternatives).