Hi there,
I'm from Kaluatra - Sri Lanka and I'm using both Dialog and Mobitel.
Cost of plan - Startup cost is almost same on both carriers but they have different packages at different prices.
Network coverage - This is also same on both carriers at most of the time in here at Kalutara. But when it's come to 3G or 4G coverage, I have got better reception on Mobitel.
Data limit - In this segment, Mobitel scores more then Dialog. Mobitel has more data limit than dialog in most of their data packages.
Data speed - I have mentioned it above.
Customer service - In here, Dialog scores than Mobitel. As per my experience, Dialog agents are aware of most of their new stuff than Mobitel.