What do you think is the best way to go? I know that if you are trying to sell something the best way to go is to try to get visitors email, but if you are promoting a pay per lead offer i don't think that is the best idea to try to get visitors email twice. Apart from that its heaps more easy to direct link to the merchant.
In my endeavors i use a combo of both with different niches but same keyword loading. the key to the loading of keywords is to stay within a 10-12% range. Overdoing it will keep you in the bottom tier of PPC engines.
I'm on a public pc right now. But I think if you use any type of keyword producing program it would be able to give you a percentage count of how often a certain word or group of words have been used. try this for starters: https://adwords.google.com/select/KeywordToolExternal
For natural search results you definitely want your own landing page. You'll never get natural visitors without it. For PPC here's the ups and downs. No-Landing Page PPC Pros - Very Quick to Market - One-step process (conversions are more likely than a 2 step process with landing pages). No-Landing Page PPC Cons - Quality score may be low. - Very hard to compete in search CPC. You have to beat out all the same people with the same display URL for your ad to show. - You can't brand your site. - No direct type traffic. (Some people just type the display URL they see in an ad). - Landing pages quality score (also page rank) goes up the older the page and domain is. (This is my personal theory here). - Never get organic/natural visitors. - Cannot up-sell visitors. - Can only offer 1 product instead of having the option of 2 or more. - You can sell landing page domains if they have history.
I like the quick concise info provided with this post. Key factors are addressed and weighed against very good. Rep coming!!