Pengaruh karakteristik nasabah moderat terhadap preferensi produk bank syariah dibandingkan bank konvensional : studi kasus nasabah PT Bank Muamalat Indonesia Tbk, cabang Kalimalang-Bekasi = The effects of moderate customer's characteristic to the preference of sharia versus conventional banking products : a case study of PT Bank Muamalat Indonesia's customer of Kalimalang-Bekasi branch