Both transaction will take pretty much the same time to process. It will depends mostly on the transaction fees they paid to be included in the next block as fast as possible.

Also when Bitcoin are sold on exchanges they don't transact on the blockchain. That's done off chain. That is transaction done on exchanges aren't written on the blockchain.

If you're interested to learn more about how Bitcoin works and thus most cryptocurrencies I recommend you read my piece on Bitcoin. The explanation about how Bitcoin works begin under the subtitle Bitcoin.

https://steemit.com/joy/@teamsteem/fully-enjoy-this-moment