I don't think there is a price difference but I could be wrong. I would go with the x39 if it were me. Classic Russian round with the Russian gun and ammo is cheap.
Mine is in .223 and I wish it wasn't. I should just try to trade it.
Second AR is half finished. I just slapped the same lower from my other AR on it to get a visual of what it would look like. The stock will be a collapsible M4 style. I like the simplicity of it. Now I'm just waiting for my parts to come in. With all of the panic buying of late, I don't even think the parts have shipped. I rushed and bought them the night Dicks announced they were pulling the ARs because I was afraid people would panic and buy everything.