During attorney review, the executed contract can be ratified, modified or cancelled within the provisions of your contract. So if you want out of the deal, your attorney can kill a deal. Is it worth it? If you have another buyer really interested, have him write it up formally and compare apples to apples. Besides sales price, earnest money, down payment, conventional or FHA loan, home sale or closing contingency, closing date, and home inspection repairs, (as-is).
Usually there is a five business day provision for attorney review, so that is your window to kill first offer. But why? Unless someone comes in significantly higher, then you risk house not appraising out and the deal falls apart with buyer #2. Strength of non price factors should be the primary reason to look for an out with a contract. Talk to your local agent and attorney.