they're similar with slight difference. litecoin has faster transaction times, shorter block times. dogecoin has much more coins per block so it is viewed as a "fun" currency.
Then what you recommendations between bitcoin, litecoin, dogecoin? Which one is better in terms of profit?Although they are almost the same but I think it looks like in terms of the amount of their expenses differently
it depends on what you mean by profit. In terms of mining profit, they run different algorithms which suit certain processing units. let's say you have CPU, litecoin would benefit you more if you mine. however with asics these is pretty much redundant. But making use of difficulty levels and exchange rate, it is possible to benefit more by mining these altcoins. multipool has an automatic feature that mines the most profitable coin.
regarding trading or as a kind of investments, Bitcoin is pretty established while the rest are not, they have higher potential of a rapid increase in prices, however, they may also flop. no one knows for sure so it depends on whether you think these coins have potential. One example would be during the previous bubble, litecoin gained much more in value compared to Bitcoin but crashed harder
