With twins, I'm definitely doing buckets (already have them) as I want to be able to attach them to a double stroller for logistical ease in a lot of places. Also, since I want to do three seats across at first, at least the middle seat really benefits from being a bucket as it is hard to strap in across another kid, even my FF DD. But even without twins, I really liked the bucket for DD too for a lot of reasons. The winter one is pretty obvious, it is really nice to get the baby all bundled up inside and quickly snap them into the car, but even not in the winter I loved the bucket because it was easier to get her in the bucket seat strapped in then trying to do it in the car. It is nice in a restaurant to have a place to set the baby down for a minute or if they stay asleep, we always ended up taking DD out quickly as she wanted to be held all the time, but it was still nice for her to have a "seat" before she could sit up. Same for the pediatrician, I would put my purse and coat and her blankets and whatever else into the carseat and carry her, so it was like a shopping basket. I never had a stroller it could strap into, so I can't speak to that, it seemed like a waste of money to me with just one, especially born in the winter. And yeah, if the baby is sleeping, it is very nice to be able to carry them in and not wake them up getting them out. As for getting used to that to prepare for a convertible, if you have a bad sleeper like I did, every minute extra of sleep you can get is golden, so the bucket was worth it for that alone! And also for DD as she got bigger, she didn't wake as easily, so it wasn't as big of an issue to take her out of the carseat. In fact, once she started to actually like the car, we used it to put her to sleep often and then take her out and put her down in her crib, but that kind of stuff you never know how your child will be.
They are heavy though and that can be hard for a lot of folks, especially if you have a big baby. My DD was small (5lb4oz at birth), so I liked the bucket as she fit so much better in it than a huge convertible. Convertibles seem to be a bit better now about that now, but still they are so huge compared to a tiny baby. They are also another expense and even with some benefits they are often not worth it which I totally get. Also, I loved using my baby carrier with DD, but I still liked the bucket for some things anyway. Now I figure I will end up doing some wear one baby and tote the other in the bucket or snap both into a double stroller depending where I am. If I can get the hang of wearing two, I'll do it, but I imagine it might not be easy at first!