It depends on model.
If you mean SHV-E300S/K/L, the there is no reason to buy it now. There are no advantages comparing to GT-I9500 except LTE which will work only in Korea.
But if you mean SHV-E330S/K/L model then it worth to think because of faster CPU (SD800). Also this model is fully compatible with GT-I9506 by firmware. You can flash system.img.ext4 from I9506 and get normal international version without any Korean pre-installed apps and won't have SMS problem.
But you always has to care about cellular frequency bands compatibility with your region before buy!
Samsung Galaxy S4 SHV-E330S: Optimus ROM (TW 4.2.2) & Kernel. CPU OC 2.7GHz, GPU OC 645MHz.
Samsung Galaxy S4 GT-I9500: Optimus ROM (TW 4.3), Perseus Kernel. CPU No-OC, GPU OC 700MHz
Past models: Samsung Galaxy SIII SHV-E210K & GT-I9300, Samsung Galaxy SII GT-I9100.