For someone on the artistic/creative side would it be easier/better overall to use Wordpress.com : get a webhost & install Wordpress.org on it or to use the webhosts building software ?
This question I ask for my niece who is a relative beginner at building websites.

Setting up a WordPress.com blog is always going to be easier than installing your own copy of WordPress, regardless of your skill set or inclination.

If by artistic/creative you mean someone who would be interested in designing and coding their own theme then WordPress.com isn't an option since you can't upload your own themes or plugins.

How would you install worpress.org????

You can download wordpress the software and install on your own domain which gives you more freedom in what you use it for.
Also by installing Wordpress 3 you can set it in multi-user mode and run multiple blogs on your own hostname.

Just as everyone has said before...If you install it manually via your own server, you'll have more customized options. Templates and such become more easy to manipulate and you won't have to follow the strict nature of Wordpress.com.