Zawnet has it correct I think.
4 birds with UFO dome, and seat numbers conforming to the generic seatmap published. 2A/K real windows. 9M-MTU,V,W,X
2 birds with newer layout, no UFO dome, seat numbers not conforming to the generic map. 2A/K are actually aisle side seats. 9M-MTY,Z
Personally, i do not like the 4 older birds. I sat in 2K on MTV over the weekend and I felt exposed where my legs were. There's very little storage area and it feels somewhat cramped at the armrest area.
The 2 newer birds (of which IMHO 3 "H" is the winning seat) have proper tables to put your stuff and it just feels that bit more spacious.