okay, so im trying to rank high in a very competitive field, and I think its good to use your main keyword in your domain. so, will it effect my ranking if lets say someone search for dog screen savers all else being equal, which will display first? mydogscreensavers.com OR dogscreensavers.mysite.com ?
It depends on how well indexed your main domain is, and how many links you have to your site. If your site is new, and you try to build up a subdomain, it will take time before your result will show up. If so, try using Wordpress instead for your sub domain. The reason for why Google loves blogs is the automated ping extensions. In this case your site should be indexed really fast and start appearing in the SE. If your main site is old, and you have a lot of incoming links, then you should go for the subdomain.
I cant use wordpress for what im trying to do. So your saying im better off going with individual domains?
No I'm not. If you have a quality site, there should not be any reason for why you cant get a high ranking is you use this: www.mysite.com/keywords. What I'm saying is that if you want to use a subdomain, then remember that your subdomain will act like an individual domain. Anyway, if the competition is really hard, you will have to use a lot of time on on page optimization, and then get quality links to your site.
I was told its MUCH easier to get top 10 with just the domain, as opposed to mysite.com/yadayadyada/keyword/keyword.