They are essentially a good Hookah type bowl but they should not be used to smoke every type of shisha. They are a good starting bowl to learn how to pack correctly but should be used in combination with a more dry tobacco blend to prevent leakage. The top recommended bowl are the phunnel bowls. They allow for easier packing (if you buy the harmony type, which is a more level bowl than the ones cut at an angle) and keep all the shisha juices in place throughout the session. The phunnel bowls are also simpler to clean up afterwards. The vortex bowls are best left for the experts or those who have more experience.
As far as glass or clay bowls go, they are considered to be almost equivalent when it comes to delivering a good smoke but each one has its advantages. Glass bowls are slightly higher in cost and take longer to heat up but are sturdier and fun to see in action. Clay bowls are harder to keep clean but are easier on the wallet. You can always buy one of each and try out a session or two to see which you enjoy more. The small details, such as size and number of holes in the bowl are only slight variations that have no large impact on how well your shisha will taste or smoke. Outward designs are also an individual preference.
Buying from a trusted retailer will ensure you get a functional and tusthworthy Hookah bowl that will meet your specific needs. Do not be afraid to do a bit of research beforehand and ask all the questions you have in order to get the best bowl. It is also wise to know what type of shisha you will be smoking on a regular basis before selecting the type of bowl. A shisha that is juicer and has a bigger cut (larger pieces of stem and tobacco leaves for example) requires a deeper bowl for instance.
Knowing your shisha will allow you to choose the most appropriate bowl. What will count more towards an awesome Hookah session is the quality of shisha purchased, how well it is packed, and the cleanliness of your Hookah accessories. Hookah is all about personal preferences and each individual person will have their favorite bowl to smoke from given enough time. All it takes is practice and maybe a friendly guide to get you started towards the path of Hookah smoking.