The advantage of a glider is that you can’t experience an engine failure. So it seems, you avoid any bad surprises, and there is no safer way to fly than on a glider.
Flying a single engine airplane gives you the freedom, but there is always a risk of engine failure. In this case your plane turns into a glider with not the best performance, as it is heavier and it has not the same glide ratio as a glider.

Glider “Blaník”, reg. OM-2709
In my opinion, having some experience on a glider makes you a safer pilot, in the case you experience some problems with your engine, you are used to handle this situation with less stress (the engine failure is a part of a PPL training as well).
I took a couple of lessons on a glider and I really enjoyed them. This particular flight was made on Blanik, registration OM-2709, and the first difference you note is the silence. There is no engine, so you hear only the air soaring. Second advantage: the views… You feel like a F-16 pilot enjoying the views through the big canopy. 🙂

The views through the canopy are realy great!
There are some small differences between flying an plane and a glider, if you turn, you have to add some rudder. If you are sitted in the front, and you stall it, it feels different, as the nose is much shorter that in the plane. You also can’t apply the usual throttle, but the recovery is pretty fast.
If the thermal is sufficient, you can stay airborne for hours (in my case there was no thermal, so we went down pretty fast…), so don’t pay the fuel and the flight is cheaper!
Flying a glider, you can enjoy the views like this:

Getting towed into the skies, other Blaník in front of us (above the towing aircraft)

Letisko Očová – Očová Airfield
The units of measures are meters instead of feet and km/h instead of knots, but as the numbers serve as a reference, this is not a big problem.

Cockpit of Blaník
Here you have a short video as well of soaring in the skies.