We have two brands of in-wall toilets. The best known brand is Geberit with the systemfix, the other brand is TECE. 
Geberit is well-known for their in-wall toilets, because they are also good and of high quality.
The TECE toilets are fairly new in Belgium, but very well designed. The important thing is the slightly larger hole to replace parts more easily. 

Your choice will depend on which push plates you like best, because the quality is the same.