The tank above is an example of a rimless tank from ADA Gallery in Niiigata, Japan.
What used to be costly has now become standard in international aquascaping circles. Rimless open top tanks that flush with a matching a cabinet give a clean, seamless look that blend in well with the surroundings and gives minimal distraction to the aquascape, especially when the water level is filled near the brim. Matched with a well designed aquascape - the aesthetic presentation that rimless tanks give is superb.
Rimless tanks also allows a more seamless transition for tanks that have hardscape or plants that rise above the surface of the tank. This is especially applicable for wood scapes; many mosses and plants can grow above the water surface.
The main downside to this approach is that you cannot keep fish that are jumpers. There is also increased evaporation (but better gaseous exchange) due to lack of cover. If you are looking for the lowest maintenance possible, then topping up water regularly due to evaporation may be a significant consideration.
Such setups are best paired with lights that can be hung high - such models may be costly as well. This gives open space for one to work on the tank as well.The photo below was taken at Sumida Aquarium in Tokyo. Emersed plants include Bolbitis heterocilita and Amazon sword plants.
Crystal glass/low iron glass has higher clarity and has a light blue tinge compared to the green tinge of normal glass. For aquariums with thicker glass, (8mm or more), the difference in clarity is significant and worth the investment. Aquariums will appear brighter and colors more vibrant.
For small tanks (10 gallon and below) with thinner glass, the effect is less noticeable. Crystal glass will often cost significantly more. However, the clean lines and clarity of rimless crystal glass tanks greatly increases the aesthetic appeal of aquascapes. Crystal glass is slightly more delicate than regular glass and chips more easily if hit by rock (for example during aquascaping setups).
Starphire/PPG - Higher quality version of low iron glass. Most neutral tint and highest clarity but also costs the most.
Acrylic - Only half the weight of glass, with joints that can be chemically fused. This is often the choice for very large aquariums that require strength of construction while minimising weight. However, it is more prone to scratches. Also costs more than glass tanks.
Seams- Check that the silicon work is uniformly applied and that the glass edges flush smoothly at 90 degree angles.