I just wanted to add my two-cents worth, based on my experience on Nauset beach:
Manufacturers have figured out that 95% of the people buying SUV's are never taking them off-road, so now they are starting to build them for the soccer mom set. Soccer mom SUV's are not good beach buggies.
Everything that makes a rig good for the road, makes it bad for the beach.
The most important factors for driving on the beach are, ground clearance, torque, and tires. Horsepower don't mean squat. You want a buggy with lots of ground clearance, big wide tires, and plenty of low-end torque, preferably a very wide torque curve.
Four-wheel drive low, is not meant for getting unstuck after you get buried. It is designed to lower your buggy's overall gear ratios to give you a better selection of usable gears, which will keep the engine in the usable torque curve.
Another thing you want to consider is the track width. The deep tracks on the beach are made by full-size pickups with heavy campers on them. A small narrow buggy will run with one side in the tracks, and the other side up in the middle. This is not a good thing.
You can forget about any sort of all-wheel drive car, you can not even get a sticker for it.
Manual transmissions are preferable to automatic transmissions. You can select the gear which keeps the engine in the torque curve.
Buggies I have seen stuck on Nauset:
Ford, Chevy & Dodge full-size pickups( Probably too lazy to let air out of the tires.)
Suburbans( Ditto)
Suzuki's( Too narrow, tires too small)
Isuzu Rodeo, ( Not enough ground clearance)
Keep in mind that you MUST have a full-size spare to drive on the beach. This is the problem with the Isuzu Rodeo. The spare tire hangs down well BELOW the rear differential, giving the rig about 6" of real ground clearance. It is like having a rear-mounted snow plow on your buggy.
Cargo capacity is good too. If you leave the beach, you can not go back on for six-hours, so if you forget water, food, etc, you are just plain stuck without it. If you plan on bringing a non-fishing spouse to the beach, they will need to be comfortable, in order to insure that you will get plenty of fishing time. This means things like big coolers, chairs, grills, tables, wind screens, etc.
To summarize, think big tires, wide track width, manual transmission, lots of suspension travel, stiff springs, cargo capacity, and low-end torque.
And please remember to lower the pressure in your tires to 10-15 psi so you don't chew the beach to shreds!