Hmm... Both flights are operated by 777-300ER's (77W). CX's 777-300ER's come in two layouts, 77G and 77H. 77H is a 4-class plane with F, J, Y+ and Y, whereas 77G is a 3-class plane with only J, Y+ and Y.

I'd say that the state of CX's 777-300ER's are hit and miss. CX has been taking deliveries of 777-300ER's since 2007 and they received the last of this type in 2015. So the plane you receive on your flight could be anywhere between 1 to 9 years old. In theory, you should have better chances of receiving a newer plane if your flight is operated by a 77G, since this type only started to exist in 2012. However, receiving an older 77W doesn't necessarily mean a tattier cabin because they have undergone interior refurbishments 3-4 years ago when the 77H configuration was first launched, which is also a period of time when CX's newer 77W's are being delivered.

I'd say that the condition of seats on your plane is not entirely matter of the plane's age, it has more to do with how well the seats on the particular plane has been maintained. You could receive a newer 77W with the seat falling apart due to QC issues that were overlooked during the manufacturing process. Age does play a part, but it's only one of the variables in determining the cabin's overall condition.