If you are travelling in Y the pitch on EK is better than TK.

On the other hand, depending on your class of booking, miles earned might be quite a bunch.

The J lounge in IST is far superior to the DXB one, and not sure if PP grants you access to the EK lounge anyway.

IMO it's all about the schedule (lenght and flight time), and only you can ascribe a real value to that.

Personally I would be annoyed by the extra stop on EK and the longer route to DXB (12.204 miles vs 11.583 one way)

Soft product is reasonably similar for what in Y is worth, and both hubs are busy with frequent circling and bus position arrival.