If you are a winning cash game player, you will always have the highest winrate by buying in as deep as possible. This is because, bigger mistakes can be made with deeper stacks, and since you are better than your average opponent, this will tend to benefit you in the long run.
If however you are a learning player, it can be argued, that it is just the other way around. Maybe it is then better for you to take away some of those difficult spots, because you will make at least as many mistakes in them as your opponents. It depends however also, what is your main priority? It is important to win the most right here or now, or is it more important to maximize your learning?
Finally buying in shorter will decrease variance, which can sometimes be good, if you are taking "shots" at a higher limit. If for instance you see a table in the lobby, which look really juicy, but its outside the limit, you normally play, then why not buy in for minimum and sit a few rounds to see, if it really is as good, as it looked. If not, then maybe no need to risk getting stacked by a tough regular, while you are figuring that out.
If you are talking about live poker, then preflop raise sizes are often huge, and I really would not bother buying in for less than 100BB. If you are not bankrolled to put those 200$ at the table, then play online instead.