It is certainly a personal preference. I think Valor has the best looking flame, especially in their large unit.

I remember being told by a retailer that Valor is the gold standard and probably the most expensive of the direct vent systems. But the gas logs by Eiklor, which are not direct vent but vented (NOT VENTLESS) produce the most dramatic dancing flames I have ever seen. But we opted for a Jotul direct vent gas insert and are very pleased with it. The flame is real-looking but the really dazzling appearance of the Eiklor. But the Eiklor is not energy efficient.

It depends on your priority. If you live where the climate is mild and you do not need really serious heat from your fireplace, consider the Eiklor. But if you're comitted to "green" issues, get a direct vent system.