There are many things to consider, but the most important is that the contractor knows the proper hardware to use. It should all be Stainless Steel, if the contractor says anything other then SS, find another. Many decks have pulled away from the house, or came free from the support posts because the lag bolts, or deck screws rusted so much, they actually disintegrated, and the deck failed. The other thing is that all the supports, and ledger board attachment to the house is glued as well as nut & bolted into the house, not lagged. The cost to make the upgrade to SS hardware, and use of construction grade adhesive on an average 10’ X 30’ deck is about $160.00, a small price to pay to know in your heart, that the deck you build will always be as strong as the day it was installed.