Most deck plans you find online assume a 40-pound live load and a mild winter. In the Roaring Fork Valley, design snow loads run from roughly 50 pounds per square foot in Glenwood Springs to 75 or more in Snowmass Village and Redstone, and a deck that isn't built for that will sag, pull away from the house, or fail at the ledger.
The fixes are all structural and all invisible once the decking is on: bigger footings poured below frost depth, beams and joists sized for the local load, tighter joist spacing, and a ledger fastened through to solid framing with the flashing done right. None of that costs much more than doing it wrong, but it can't be added later.
Material choice matters too. High-altitude UV bleaches and checks untreated wood fast, so composite decking or a good cedar with a real maintenance plan will look better in year five. Railings need to meet code height and baluster spacing, and if you want cable or metal, the posts have to be set for the extra tension.
Finally, think about how the snow leaves. Decks that shed toward the house rot the siding behind them. A slight pitch away from the wall, a gap at the ledger, and downspouts routed off the deck keep the structure dry and the house wrap intact. Ask your builder to show you these details on the estimate. If they can't, keep looking.