Its not all the same at all
If you wax your car you will notice how long the wax is lasting depending on what shampoo your using, I certainly do, cheaper shampoo will strip off the wax and appear to be cleaning better, its all about the paint prep before you even get the car dirty, ive found autoglym to be pretty good for my needs, doesnt strip the wax off and you only need a cap full in a bucket of water, I got it in a 5l bottle for about £15, its lasted me 2 or 3 years so far.
The effects of different shampoo will be much less noticeable on clear coat paint though.
If your not into waxing your car, you should just buy the cheapest shampoo on the shelf, or get down the koso car wash with a fiver like I do when my daily driver is dirty
