What makes for a better domain name, a hyphenated dot-com like “Cheap-Domains.Com” or a “clean” dot-net name like “CheapDomains.Net” with no hyphen? To find the answer you first have to ask yourself what “better” means in this instance. Better for what? What do you plan to do with the domain?
Are you just planning to register and park it with hopes that people will stumble across it by accident and hit on an ad or two? If that’s the case than forget the hyphen; people aren’t in the habit of typing hyphens in the address block and you won’t see much traffic. But keep the dot-com if you can; dot-nets aren’t exactly second nature for address-block typists in the real world either.
Planning to auction it off with hopes of a high price? In that case the hyphen will probably weigh it down; for better or worse, the people who make the market in domain names have decided that hyphens are a negative influence on price. A dot-com is usually preferred; but burden it with a hyphen and the same domain name with a dot-net would be much better.
Or maybe you’re planning to build your business website around the domain name? If that’s the case than be careful with the hyphenated name. If you have to use a hyphen that means somebody else already has the clean dot-com and you don’t want to do his advertising for him; he will likely get the most benefit from address-block searchers. It’s possible to run afoul of the trademark laws too; a name like I-B-M might cost more in legal fees than you could ever hope to make with it. Go with the dot-net or even a dot-biz or dot-bz.