I'm not saying one is harder or easier but you should only look at any dps check boss in last 3 years and see how the first kills looked in both sizes. In 10 man they always had time to spare while first 25 man kills were in very last seconds by the skin of their teeth. When bosses are tuned differently all 'ratios' and 'math' don't matter. Can you find me one dps race boss that had tighter enrage timer on 10 man?
Rag heroic P3, Ultraxion, Spine tendons, Gara'jal...dps checks were much tighter in 25 man. Again, I am not saying they were easier or harder cos that can depend on many other things but seeing people claiming that dps checks are tighter on 10 man is ridiculous.