Know the value of the 405 Baja. NADA gives a base line. Used boat values are not apples to apples. Condition, equipment, hours, area the boat was used in, and area the boat is being sold in all play a part in the value of the trade-in. I have seen boats that value low in NADA sell for 20K more because of condition, and availability. When you find the boat you want and your at the table negotiating have a knowledge of the realist value of your boat and compare it to what the dealer is offering. Also have a realist value of what the new or used boat's true cost that you are considering purchasing is. Compare real numbers to real numbers. With that information make a decision to trade or not to trade.
Typically a dealer wants numbers to look like 10% to 12% margine on the sale of new boat and 30% gross profit on the trade-in netting 10% to 12% margine on the trade in. Doing your homework helps you from leaving money on the table. Everyone needs to win.
Trade-in verse selling to private party. Many States deduct the trade-in value of the boat from the total cost of the purchased price. Example 210,000.00 purchase price 100,000.00 trade-in, 6% sales tax, tax collected on 110,000.00 instead of 210,000.00 savings of 6K in sales tax. Keep this in mind when making your decision. Good luck in your search for the Ranger Tug.
New or used ? That depends on the availability of the boat in the used boat market that you are looking for. It also depends on how long you plan on keeping the boat (depreciation). The new boat has a warranty but honestly that doesn't mean much. Most likely most of the small things you will be fixing yourself. If you buy new or used have it surveyed by a good reputable marine surveyor, boat equipment, hull and power plant. Any issues noted have them repaired before closing the deal and taking delivery. The used boat will be less cost, less sales tax. New or used purchases are usually a personal preference.
Going from a 405 Baja ,predecessor 38 special (Nice boat) to a Ranger Tug (Nice boat) is quite a change. I would highly suggest a sea trial with your family on board. The water and sea's you are accustom to cruising at 40 mph in your Baja you will be cruising in at 10 mph in the Ranger. You probably will not be cruising at 30 mph in a 27 ranger with your family in 2' to 3' sea's. It can, but it's not going to be comfortable. Completely different boats + 13' longer (405). Don't take that statement as the Ranger is not a sea kindly boat. It is, just considerably different from what you have now.