Top ranked coins or the so called strong coins are good to invest when the price of bitcoin is surging because they can still able to go up and not so affected by price rally. Low ranked coins are profitable when the price of bitcoin is steady or moving slowly but they tend to go down if bitcoin is uptrend. Before investing in any coins, analyze the market and the coins you are planning to buy first.
Right, top ranked coins guarantee safe to be a long-term investment, if the marketcap has reached more than $ 1 billion then devs. have a large capital power so that they will keep the coin from dying.