For easiest care and least worry, adults seem to be best. But they take and need more space, so if space is a limiting factor, babies provide a window with which you may acquire more space. Also, if you want to watch your tort's development, from hatchling to adult, an adult cannot indulge you there, no matter how it tries.
I would think it depends on balancing your wants with what you would feel most comfortable and happy taking care of.
Hi there, it depends on the person. I wanted a baby because there's the satisfaction of raising a tortoise to adulthood, but then again I have owned reptiles before and was confident with my ability to care for it.
Aside from that, there are advantages in buying an adult or subadult. The sex can be determined in most cases if you want to breed and less worrisome in terms of care. But you will have to have space ready, whereas a baby will require less space and give you time to prepare. Also for adults, the colors and shell pattern/pyramiding are later in the stages, whereas a baby it fully depends on how well you care for it (excluding the colors and patterns of course).
Looking back, I don't regret my decision at all. I have seen my tortoise go through stages as a baby, which I find interesting.
Depends, but for most folk a sub-adult to adult is easiest...many neophyte tortoises can be pretty delicate, so much so that even experienced keepers lose one from time to time.