The 6SN7 is a better sounding tube as its easier to find examples that have lower microphonics. IOW the 6SN7 was designed for audio.
BTW the 6C33 power tube has been out of production and the plant that made them dismantled for about 19 years.
BTW the 6C33 power tube has been out of production and the plant that made them dismantled for about 19 years.