For a flight to/from SIN,
Left side is a safer bet. On landing to 09, you get to see Kuta Beach. If you use 27, you'll see Tanjung Benoa/Nusa Dua that Chris KSDF took.
Sitting on the right would give Jimbaran Beach and Benoa Harbour on 09 and 27 respectively. Too far away.
For approach, left is better, because if you use 09, you'll go down the whole of the western side of Bali for the approach, on your left (right is just pure sea). If you use 27, there are 3 ways they would do this... circle the north east of Bali (island on the right, Lombok in the distant left), or go on the downwind between the airfield and the mountains (left you get the mountains, right you get the airfield and city), or you circle around the south peninsula (then sit on the left).
But for take off, sit on the right, you'll get a good view