IMO I don't think that it really makes a difference with the customers as long as it smells good, some may go for the hype about soy being cleaner burning, and supporting the american farmer, but in a whole I think if it smells good to them they are going to buy it either way. My suggestion is to sell both and see which sell better in your area, then go from there. I don't find it costing me anymore to make soy candles, except that you may have to double wick, but the cost of that extra wick is so little that it just doesn't seem to matter to me. I also don't find that I use anymore FO or color, though I am not really looking for the dark bold colors in my candles as of yet so that may change.