Does Twitter have any short name like Facebook's
fb.com? It would be easier to advertise Twitter accounts like Facebook pages.
twttr.com redirects to
twitter.com, so you could use
twttr.com/accountname. But that only saves two letters and may not be recognizable to some.
@accountname format is pretty universally recognized as the format of a Twitter account. That's what I'd use.
t.co is Twitter's URL-shortener and wouldn't be useful for this.