The differen between W2 and corp-to-corp is in who assumes liability to withholding taxes. For a W2, the company thay pays you must manage it. If corp-to-corp, the corporation (yours, presumably) that pays you manages it.
When paying through W2, a corporation pays additional taxes. In the US, this extra overhead includes matching the employee's withholding for Social Security benefits and Medicare. There may also be additional withholdings levied by the state, such as unemployment insurance.
Unless you have a corporation of your own already set up, you're probably better taking the W-2. It's a lot less work at that point.
Make visible what, without you, might perhaps never have been seen. - Robert Bresson