Up front costs for new homes are generally higher; on average, you pay more for a new home versus an existing home. Insurance an a new home is in general lower, no renovations or repairs are needed, more energy efficient windows, better insulation and smart appliances, usb outlets, open floorplans. If you buy the house before construction, you have the advantage of choosing your own floorplan, style of the kitchen, flooring etc.
Existing homes have the advantage that the location is usually in an established neighborhood. Schools, stores, doctors etc are typically established in the area. Lot sizes are in general larger, so the houses will have more distance between each house. Mature trees and greenery is another advantage. If your budget allows for an existing home, be aware of maintenance down the line. An older house may be lower in price, but chances are that you will have to budget more for repairs, replacements or even renovations.