I understand about making long car trips with a dog. Once our rescue, small/medium, cross/breed gorgeous girl had settled down with us, we travelled - 7 months later, in the summer - from Somerset to the Highlands, however we broke the journey up twice, by staying in travel lodges, there and on the way back. When we got there we camped, she loved the whole process, but she insisted that we all went to bed - well to our blow up double mattress and double sleeping bag - at almost 8.00pm on the dot, probably because it was getting chilly by then! We then made the same stops on the way home. (By the way, she was not a designer cross/breed; according to her vet, she was a Jack Russel, crossed with something a little larger that a Jack Russel, but probably still a terrior type).
Sometime after our sweetest girl had to be put to sleep, we got a male Labrador puppy, he was 12 weeks old, we had met his Mum and Dad and some of his siblings in his amateur breeders house. The breeder had registered him with the kennel club, and their vet had done all the necessary labrador health checks. He also came with a months insurance, and a supply of the dry food they had been given him ("Oscar' I believe). He also trembled all the way home, but didn't make any sounds. Within a couple of days he was jumping small gaps between family members knees, and nipping his human families ear lobes and noses, which was delightful, but we gave a little sharp squeal, and said a firm no, and put him down for a couple of minutes! Once he grew out of that he never nipped anyone again. I can't actually remember him ever growling either.
I don't want to be argumentative, or annoy you, but I probably will when a ask as gently as possible, how do you know that your puppy didn't suffer at all on that first trip? She was in a crate at the back of the car, so presumably you couldn't see her, so you can't be sure that she was actually asleep, and not scared? Also, what is the likelihood that a small puppy being taken away from it's Mum and siblings, and the only home it had known, by people that it might not have even remembered from their last visit, would be at least nervous, and maybe very unhappy?
If you do reply to this @CoubousAndTourmalet I will hopefully get to read your reply, but I probably won't reply again, as I don't want this to turn into an ongoing discussion on @AmpleLilacQuail's thread. I certainly have no intention of being rude, so please don't take me as being so. Also, and possibly unfortunately, I am old enough to know that any arguments you or @LandsharksAnonymous make, will not change my mind, as I have had a great many years to hear and think about lots of different peoples' thoughts and beliefs. I am not impressed by how much time and distance someone travels to get their puppy, if it is much more than an hour, or an hour and a half at a pinch. Letting a very young puppy, who won't have had all of their vaccinations yet, outside at motorway services, or wherever, is definitely not a good idea either.
I am very impressed with the OP for wanting to garner as much information as possible before making her choice about which dog is right for her, and I think that including the views of people who love dogs, through Mumsnet, was a very good idea. It will have definitely given her food for thought, but I do hope that she hasn't been put off the idea completely, and that whilst taking in the pros and cons that other people have helped her think about, I do hope that she won't let her gut instinct about which dog is right for her, be totally extinguished by other people, especially those who might have ulterior motives for not liking certain other breeds.