EK's Y seat is narrow, but has good legroom - around 34" which is pretty hot.

As commented above, both locations are quite dull. If you've never visited the Middle East, I'd recommend DXB as if you takwe a few hours to tour around the souks and creek area you'll get a 'lite' experience of the region.

The food is better in SIN, and there is enough to occupy you for 24 hours.

And if you are not going out the airport, either are fine with great facilities outside the J/F lounges. SIN maybe slightly nicer.