CDMA can give trouble free traffic and will not result in a break down of services. On the other hand many applications and high technology is available for GSM which is more popular as compared to CDMA. But due to heavy traffic at peak hours, your SMS may not reach the intended recipient in time. Bulk SMS may be difficult to send. Therefore there are advantages in both. As possessing more than one cell phone is common now a days, it will be best to have one GSM and another CDMA phone.