A robust data delivery system between a server and a mobile client uses the Short Message Service (SMS) and General Packet Radio System (GPRS) services. A user and/or messaging provider set preferences on the mobile client for service coverage estimation that balances SMS and GPRS service coverage estimations for the mobile client, and/or service selection preferences that are expressed using a balance of cost of service and reliability of service. The mobile client receives a message from the server, sent using either the SMS or GPRS services. The mobile client checks the status of its SMS and GPRS signals. The mobile client weighs preference settings and the SMS and GPRS signal statuses to decide whether to answer the server using SMS or GPRS. If GPRS is selected, then the mobile client answers using GPRS; if SMS is selected, then the mobile answers using SMS.