Difference between cooking vegetable curries in a pressure cooker and a wok?
I am not sure if you are asking about pressure cooking vegetables or just using the pressure cooker to cook. If you are talking about pressure cooking the vegetables, I think a kadai is more suitable because it preserves the texture of the vegetable you are cooking. If you cook the same vegetable in the pressure cooker, it is difficult to control the 'doneness' of the vegetable. 

For example, I have cooked aloo mattar (potatoes and peas) in a kadai and in a pressure cooker. The peas come out much more mushier when cooked in a pressure cooker versus a kadai. If I want a pressure-cooked texture in a kadai, I cook longer. 

If you are talking about cooking in a pressure cooker without the lid on, it makes no difference whether you are using a kadai or a pressure cooker.