Which class is tough 9th or 10th??

Yes, as a teacher I can close my eyes and say that Class 10 is much easier than Class 9. The same applies to Class 11 & Class 12 in which Class 12 will be much easier than Class 11. Generally, the difficulty level of Class 9 and Class 11 will be much higher than Class 10 and Class 12 respectively.
https://www.ribblu.com/cbse/papers/class-9