Well from my previous employment I learnt the soldering was better. We did civilian and military contracts and we were told to solder and if we couldnt, then we'd use crimps and connectors. We have seen plenty of cases where the crimps and connectors have gone high resistance due to corrosion and this caused it to pull so much current and heat up n burn the entire wiring. This was for vehicles.
Well when dealing with the aviation industry, you have to think weight and the large number of joints involved. Every part is scrutinied for its weight. I do not think the aviation companies would want their employees to solder all the joints. Solder joints are like welds...they have to be good and at times solder joints are studied esp for very important applications. How do you know that the employees would perform a good solder joint every time for so many joints? It is easier, cheaper and faster to crimp.
But I think for your car, solder with heat shrink tubing is fine.
I too am a electronics/electrical engineer.
When I first worked for this electronic company for work experience for my degree I had to be trained to military standard. I used to solder pcb boards that control the cruise missiles from a
milliary ship. I mean if I did one bad joint, it could mean an intermittent connection with the possibility of a cruise missile firing on its own due to a faulty controller.
Soldering is learnt skill...if you do not know how to solder well practice first.
Cheers,
Roy