Annyong Haseyo, Mr. Shin Tae-Soo.
A real pipe organ is pound for pound the most economical if one looks in the long term. A good pipe organ will last hundreds of years - you will have replaced the electric organ many times before you rebuild an organ. Each and every maker of Digital organs have their followers so it becomes a highly subjective venture as to which digital organ is the better one.
Walker Technical Company in Pennsylvania makes instruments that are quite possibly the best out there - Rodgers and Allens have a tendency of sounding "overprocessed." A rule of thumb: Any digital organ worth it's salt will have an excellent customized speaker system. The console with inbuilt sound circuits can be really whiz-bang fancy but what good is all that fancy whiz-bang circuitry without excellent customized speakers?
Hope this will help you in your quest.
Be in Peace,
Giovanni