The decision to fly/purchase a double surface wing vs a single surface wing is one that many pilots agonize over for months. This write-up is my personal opinion about double surface vs single surface wings for new pilots.
Single surface wings are slightly more forgiving for some of the mistakes that new pilots can make, especially in the way of landings and approaches, however I feel that a double surface glider is actually safer than a single surface glider, IF THE INSTRUCTOR FEELS IT IS APPROPRIATE FOR THE STUDENT. About the only down-sides to a double surface glider are that they have a higher risk of PIO, they can be slightly more difficult to land in a small field, and they are more challenging to flare properly.
PIO stands for Pilot Induced Oscillation and is usually caused by new pilots flying too fast and over-controlling the glider. Double surface gliders are a little easier to PIO because they can achieve higher speeds than a single surface glider.
If you are coming in too high on your landing approach, you can pull-in on a single surface glider and drop down like a rock due to the terrible glide ratio at high speeds for that kind of wing. A double surface wing is better able to convert the altitude to speed so while you do drop quickly, you also pick up a fair amount of speed which translates into burning up more of the landing field. If you have a nice LZ, this really isn't a concern. Most all H2 double surface wings still drop pretty quickly when you pull them in. With a little practice, a pilot can land a double surface wing in any reasonable field.
Flaring a Falcon or other single surface glider is so easy that you can get into some bad habits and end up thinking you know how to flare when in fact you really don't. Try this on a double surface wing and you'll either zoom up or land on your wheels. This issue can be worked around by using big training wheels, and spending some time on the training hill familiarizing yourself with the flare characteristics of the glider. Work with your instructor on this. At first, it's always better to start flaring a little late and ending up on your wheels than it is flaring early and zooming up.
Those are the negatives. The positives are that a double surface wing like the North Wing Horizon takes less effort to fly due to lighter control inputs, offers more performance and room to grow, and most importantly, allows you to get out of some dangerous situations much better than a single surface wing. The latter is what I want to focus on and is one of the main reasons I feel double surface wings are better for beginners.
When you are new, you learn many things for the first time. Your instructor may tell you not to go behind the ridge unless you are X-thousand feet high in order to avoid rotor and to avoid getting caught with no place to land. You may also know that you need to be aware of cloud suck. You may also be told not to fly in winds above a certain speed etc. But until you actually experience these things, your sense of judgment may not tell you to do the right thing and because of this, you may end up in a potentially dangerous situation. In addition, nature changes, sometimes without warning, and sometimes WITH warning, but you aren't experienced enough to notice that warning. If you are high above the ridge and decide to go back just a little bit to stay with a thermal, what happens when the thermal dissolves and you are left with massive amounts of sinking air, and a big head-wind to fight? You are going to have a tough time making it back out front of the ridge. The best way to avoid this is to know exactly how high you need to be for a given situation but as I mentioned before, new pilots can't always judge this so the next best thing is to have a wing with the penetration and glide-ratio that can get you out of this situation if you are unfortunate enough to find yourself in it.
You find yourself low and in sink and may not make it back to the landing zone. The double surface glider gives you a better chance of making it there. You find yourself in a great thermal and realize a bit too late that you are in cloud suck. After trying to get out, you realize you can't. A double surface glider will give you a better chance of escaping the cloud suck.
Some examples of H2 rated double surface gliders include, but are not limited to the Northwing Horizon, the Airborne Sting, The Airwave Vision Mark-4, the Wills Wing Eagle, and the Airwave Pulse.
Your instructor is the only person that can help you determine whether or not a double surface glider would be appropriate for you, and if so, which double surface glider would be best.