Here are some answers based on what constitutes a defect that can forms grounds for refusal:
1. Product defects that hampers the car's performance. E.g. Faults with engine, drive train, etc.
2. Product defects that may cause injury to the driver/ passengers. E.g. Safety features e.g. airbags, engine mounts etc etc
3. Certain cosmetic defects like dinks, dents, chipped paint on the external visible body surface.
4. Issues with internal trim that may hamper functioning. E.g. rubber seals, dashboard latch, cabin lighting, seat adjustment etc
What usually does not constitute grounds for refusal
1. Cosmetic defects on the body not visible externally.
2. Cosmetic defects in the car that does not hamper functionality
I dont think one can refuse delivery if the welds look ugly as they a) dont pose a danger to the user(s) b) Not visible externally c) hamper no functionality
In addition, the owner's manual might also highlight certain aspects that are considered 'normal' when the user might think otherwise. I can think of two that come to mind based on vehicles I have owned
- The suzuki manual (Swift) states that the breaks are noisy and basically the user should learn to live with it, it is not a defect
- The Corolla (Grande) manual states that the MID might develop some bright/ dead spots (dead/ stuck Pixels) and this is normal and not grounds for a change/ refusal to accept
Off Topic: Having owned at-least one of every type of locally assembled car at one point in time or another I can safely say that all manufacturers have had and still have issues with quality. I have lived extensively in the Gulf and South-East Asia and can safely say that vehicles there have issues as well.
Of all the vehicles I have owned the best, in terms of quality, is the Honda City. It had minimal issues, the most glaring were deep scratches on the Plexiglas covering the instrument cluster which were easily dealt with using a bog standard scratch remover.
The '08 Corolla 2.0D Saloon had the top of the dash separate from the audio system as the space was not really meant for the 2 DIN unit they were using. They really did not have any acceptable solution to the problem
The '12 Swift, apart from the terrible break screech had this annoying rattle from the dash because of the type of plastic they use. Again nothing could be done about it as it was inherent to the use of materials. I think Tiff Needle(?) pointed this out in his 5th gear review of the swift as well