The 152 is out of production and is likely never to be produced again. 152’s are used for training because they are cheep to buy, being 30 years old and have been cheap to run. As the age catches up with them and the price of fuel increases the 152 will stop being used for training.
The AT3 is designed as a trainer and will compete head on with the new Cessna, when it eventually gets uk approval. I have not flown an AT3 but I have considerable experience of similar aircraft and this class of aircraft will take over as they are the fastest growing GA sector world wide. If you are planning on getting a PPL and then buy a nice new LAS/VLA burning 15lph of mogas and doing up to 160kn, then you would be mad to learn on the old tec. It is economics, not suitability, which has kept the 152 in use well beyond its sell by date.
Rod1