My impressions? NAIA 1 is definitely in need of a face lift. Thankfully, after a few bumps, there are getting there. AC is no longer a problem. Decent restaurants, on the other hand, are needed.
JETSTAR is a budget carrier that could also be your choice in traveling. Problem is, it now downgraded its hand carry luggage weight to 7KG from 10KG. The leg room is also horrible.
CHANGI TERMINAL 1 had the monicker of being the budget terminal of SG but it is being upgraded to cater to the different higher end airlines. PAL now goes there too.
Would I ride JETSTAR again? Maybe if the price is right. But with the calculations in my head, it would be wiser and easier for me to choose PAL because of the food service and the payment options online.
Disclaimer: Wrote this post based on my experience. Paid for our tickets, meals and drinks.