Few days ago I decided to utilize some fraction of bitcoin just sitting in my trading wallet to try profiting from the market. Although I may profit when the profits was calculated in dollars but unknowingly I lost massively in Satoshi value. That means assuming I just kept hold of my coins I would had made almost the same value I made with the coins i bought. Many traders haven't realized this yet but just get carried away with the US value of their trades without realizing they lost some satosh in the process. When training, what are you mostly concerned about, to gain more profit in bitcoin or gain more in usd dollar without minding if you lost some Satoshi value?.
It really depends upon the fact whether you consider Bitcoin as your base currency or a trading currency. In case you consider Bitcoin as trading currency, it is at par with other cryptocurrencies and just another investment. So even if the price of Bitcoin rises more than the currency you holding, it doesn't matter. Suppose you holding XRP and it gains 5% whereas Ethereum gains 12%, would you consider that your money decreased because Ethereum increased more than XRP? No, right? Similarly if you consider Bitcoin as an investment then even if it rises more than your XRP, it doesn't mean you lost money.
But if you consider Bitcoin as your base currency to invest in other currencies then percentage return should be calculated on the amount of Bitcoin initially invested.