Hi Preety,
The only correct answer is ... (drumroll please) ... it depends.
What's more important to you? For future proofing, Java SE 11 Programmer I 1Z0-815 is your only answer. Are you already in or will be going to a Java 8 environment, Java SE 8 Programmer I 1Z0-808 is your answer.
You could potentially just split the difference.
Good luck on making a decision that is right for you.