I've been using the Asia package for 6 months and here's my experience
For some countries like Malaysia and Thailand, Using iPhone will require to manual use 3G else it will show 4G but WA and FB cannot use.
No such issues on Android.
Places like Cambodia and Philippines have really bad connection regardless of the phones.
At best I get H+ signal or 3G+ nia.
Its really convenient for me, cos I travel almost weekly and it's a pain in the a55 and expensive if I keep buying local sim cards.
Another plan that I am using for travel is under Maxis (Malaysia) - am using dual sim.
Its MYR188 a month, and offers 60GB data, and a daily 500mb roaming data allowance. If you exceed the daily roaming data allowance, it will auto tap into your monthly 60gb data so confirm no roaming data charges occurred. It also offers unlimited international in and out calls when you are in the markets - ASEAN countries except for Vietnam.
So I've been using their roaming data and international calls even when in Sg. Shiok ah!
Posted from PCWX using MHA-L29