it all depends on what you are going to use a boat for really. If you are the fair weather weekend angler that fishes by himself or with one guy, you can really get away with a lot less boat. If you need a boat for a family of 4 or more that wants to use it for tubing skiing etc you are going to want to go bigger. like mentioned above max hp and glass are in my opinion two important things.
The nice part about buying used is you usually get a boat that is set up and fully rigged without having to pay the retail on all the goodies, if you buy new look at adding about 3-5k for extras easily, plus in nd you pay taxes on a new boat and don't on a used one.
If you are planning on fishing a bunch of tourney's or you run the shit out of your stuff, new and warranty isn't a bad thing to consider. I bought 2 used boats when I was younger and was constantly chasing around problems in them whether it be shoddy wiring or bad maintenance that caused other problems. In 08 I said screw it and bought a brand new skeeter in Bismarck I have been running ever since and it has been a great boat, I had 5 year warranty on the hpdi and never had to use, it good deal depending on you look at it, I guess. The boat has been awesome and I know everything that was ever done to it, which is a good piece of mind I know all year it is stored in a heated shop all the maintenance is done and it hasn't let me down.
As far as keeping your money local, I used to think that was a good idea and believed what the dealership told me about getting my boat in first and priority service, then when it actually came time for them to keep their word, the service guy tells me they tell everyone that buys a boat that, but we can only get so many boats in at once. So after that episode I have no problem buying elsewhere to save the 3-7grand you usually will when you get out of ND. I know a couple guys who have been buying pro/guide boats through the years at discounted prices and would say in ND this is the way to go especially if you know who the guy is beforehand, a lot of them will let you pick what you want and how you want things rigged and run it one year eat the taxes and pass on their pro discounts to you in the fall, probably the best way to go if you are spending in the 40-80k range. otherwise biggest thing is take a used boat to the dealership or out on the water and make sure everything is up to snuff before you spend the money on it, as much as buying a boat seems like an impulse buy you should really do your homework put in the time checking boats and dealerships out,compare prices and decide what you want and don't settle for something that is a POS. best of luck