Invest, but don't overspend on your logo. One could argue that visibility is more important than looks if you had to choose. This is why you should include your logo on every piece of communication. Put it on every web page of your site, business cards, letterhead, envelopes, invoices, yellow page ads, building signage, newsletters, web buttons, promotional collateral, even small ads. If you've got a solid business and you give that logo visibility, you'll find yourself with some brand power. Then perhaps if your logo is next to a competitor's, they'll click your hyperlink. Familiarity will lead to increased sales.