Proper designing is important for attracting users. But the same users go for search engines to find their required content.
Both are important things for a site.
Which one would you give more preference and Why ?

The SEO should be implemented around good design and content. The aim should be to sacrifice little to nothing if the only gain is SEO. Generally, the more you sacrifice, the more black-hat the technique is.

I think a ratio of 60:40 should be given for SEOesign. Because google crawls your site and you get better indexing only if your content is good. But nowadays, there are lots of methods handled to get better indexing. But in general, you cant get indexed in you have your site completely on flash, but you can get indexed with proper SEO techniques.

I think both are equally important, create your site keeping your visitors in mind and make sure it correctly optimized for search engine as well.

Build your site to W3c Standards and everything will be fine

they are equally important, people often forget doing a web design is has to be search engine friendly and not just pleased human's eyes. After all what's good having a pretty looking web design but the search engine and rest of the world know nothing about your site?

Design is much more important b/c it is how your visitors will judge your company. Having good seo means nothing if the customer is just going to move on b/c your website looks bad. Thats just my 2 cents

The primary goal should be to make sure that visitors become long term customers.

If you focus on SEO instead of content and design, you will find that your long term customers will instead turn into visitors on the competition's site, and if they have better content and design you just lost a customer.

Then again, the visitor might find you (due to the SEO), but not the "competitor", hence, the sale goes to you. There needs to be a balance. Great SEO can be done without paying a significant price design and content wise. In fact, it is content that can give you the SEO edge.

I feel that both content and design are key, although SEO is where the money is. That said, you don't want to go all out on just one thing, I think it is good to strike a good balance somewhere. SEO is useless if your landing page isn't "sticky". Potential customers will just go away and you will have achieved nothing. Just an example.