Cash should not make a difference to the seller's bottom line. It can cut out some costs on your side of the equation....no credit report, no appraisal required, no funding fee, no lender fees, etc. It can also cut out some of the upfront costs as you don't need to escrow taxes or insurance.
If you do plan to offer cash, think of a way you can prove the cash to the seller. Have a current bank statement, or stock account statement, or something you can use to prove you have the cash on hand and ready to go. Offer a substancial down payment.
Try to close by year end. Depending on the bank or builder financials that may help their quarter or year to get the number off their books. It can also make a difference for your taxes as you may have some deductable expenses for this year vs next. You can also apply for the homestead exemption which will save some property taxes for you for next year, especially when purchasing a new home.
If you are buying from a builder ALWAYS use a realtor. You can look at my website under new homes for a list of just a FEW of the things we see go wrong when a buyer buys from a builder directly. As one appraiser said to me yesterday when I refered him a client who wanted an independent appraisal on a new house he purchased directly. "I can tell you right now he overpaid, why does he need an appraiser to tell him that and cost him $325?"