it's better only in a 'human' way.
normally people only remember addresses as .com.
and on keyboard, u can conveniently type the name and press ctrl+enter. .com will be parse in automatically. i always use this.
but to the robots, like google/yahoo/bling, they don't really care. they crawl and return searches no matter .com or .net
but if u're in subdomain, imo, don't bother?