I don't think you can get a meaningful answer this way. All or any of those options might be good ideas. Optimising affiliates or working on banner ads might be a good idea and there are businesses out there that make money this way. Dropshiping might also work for you. It's kind of like asking 'should I be a barber or an antique dealer?' It's not really answerable, is it?
That said, here is my opinion:
Affiliates/Banner
You are a pretty decent candidate for being an affiliate. Your site is about products and I assume your visitors have a reasonable chance of buying them. But, you need to be realistic about what your value per visitor can be on these. A conversion rate from visit to purchase of 0.1%-1% is probably the best you can hope for, assuming they are the right kind of visits, the products are good and the affiliates are reasonably "optimised". If you make $10 per sale that's $20-$200 per day. You probably know your own numbers. That is just my guess. Banners are probably going to bring in a bit less because they get a lot fewer clicks. You can't optimise them as well because they aren't yours. Affiliates and banners is very scalable. You don't need to worry about prices, sales, customer service and an extra 100k visitors will not add to your workload.
Retailing
My own preference (because of my experience and my bias) would be to think of myself as more of a retailer. This includes, but isn't limited to drop shipping. You stand to make more per visitor this way. But, it isn't scalable the way affiliate marketing is. If you get 10 times as many sales, you will have a lot more work. Customers will call you. You will find yourself between vendor and customers. etc. etc. margins can be tight and efficiency is important.
On the other hand, they are your customers and your products and yours. You can convert more visitors and make more on each sale. If you convert 1%-3% (good, but achievable e-commerce numbers) and your gross profit is $20, you can make $400-$1200 per day (less expenses, which will be more substantial).
I think that if you take this route you need to be willing to go past drop shipping if needed. You could probably stock up on a few hundred units for less than $5 per piece. You could even start your own brand. http://www.alibaba.com/trade/search?SearchText=ipad+case&...
Back to disclaimers, it isn't really about what choice you make in the sense that banners are better than dropshipping. All the choices you are looking at are reasonable. The question is what sort of business you are trying to build.