The token sometime doesn't have value on Ethplorer because Etherscan usually detect the exchange that list the token faster than Ethplorer.
Both of them are popular ethereum explorer but i prefer to using etherscan because im get used to it.
I usually use etherscan to see the gas price before send eth or tokens, so my transaction won't be stuck because the gas is too low.
Checking gas price has nothing to do with using ethplorer or etherscan. You might use etherscan to check the current gas price, while you use ethplorer to check updates of tokens in your wallet. Both have their usefulness, but people use what is more convenient for them. I use both depending on which comes to my mind first.