Hello, I want to create a new site with a domain name which includes the subject of the site. Rather than buy a new domain, I was thinking using one of my domain and add a subdomain. Do you think it is appropriate for SEO ? If not using the subdomain, I will have to buy a complicated/longer/dashed name. What is your opinion about this? Thanks.
I would go for a new domain name, a subdomain is treated like a new domain anyway however it's much easier to get links, submit to directories etc with a top level domain rather than a sub. Just be creative, there's lots of nice domains around without going for long hypenated domains.
Unless you have an idea that you're really confident about, then using subdomains is well worth considering. I have several successful 'independent' sites running from subdomains, and would get absolutely no benefit from having them on their own domain. You could always give the subdomain idea a try for a few months, if it really takes off then buy a new domain and 301 the subdomain. But then again, if it does work - there's no need to buy a new domain What sweetfunny says about submitting to directories is true though. Most directories don't want to know about subdomains. If you can find a suitable domain, get it. If not, just go with a subdomain.
Asked myself this question too. I would do the following: if the project is rather large, it's wiser to go with a separate domain name. However, if the project is smaller, you can easily host it on a subdomain.
Whether it is a new domain or sub, every thing will have to start from scratch. Points to note for sub domain are whether your current hosting can hold your new project, your current bandwidth usage. Pros' of sub domain is that you can use it as a trial account and if it is of relevancy to your main domain then it will be listed much faster.
As stated above, I seconded the use of domains, now domain prices are cheap and also directories may not accept subdomains, so that will hamper your link building and SEO
Directories are useless imo, I never include them in my link building. Here is what I suggest.... Sub-domains are for completely different content related to the main domain, if the content is related just use a sub-directory, this is the simplest way to do it.