Generally speaking sunflower lec will be less effective than soy lec.  If you've not been using lec at all, then it'll still give you a huge improvement.

Great, I just bought some from a health store to run some test batches. I have never used emulsifiers as my bars are geared towards the health food crowd and even though I don't think soy is bad in the small quantities or even at all in chocolate most people in my target market do think that.  If I can use sunflower lecithin instead and get the same results then it will appease my target market. 

No difference in comparison to using soy lecithin.

In my opinion lecithin is a very important ingredient in chocolate making for a few reasons: ability to achieve best conching results and ability to achieve desired viscosity without adding too much cocoa butter which can make product taste unbalanced and too greasy (common to high cocoa content milk chocolates on the market where high cocoa content percentage is reached just by adding extra cocoa butter).

By no difference do you mean no difference in comparison to soy lecithin or no difference in comparison to using no emulsifier at all?

We have done trials with using sunflower lecithin instead of soy lecithin. We have used liquid products with very similar specifications and there was no difference in results (taste, viscosity).

We have considered changing to sunflower lecithin to remove soy from the ingredients list but in the end decided not to go ahead. Too much effort required to change all packaging for practically no result.

I use an organic liquid version - there a few on the market. I'd add no more than 0.5% as a rule and slightly less. As another poster commented - the taste is not fabulous - but then again it is for emulsification not taste, hence the small amount. I use because most soy is GMO. 

I purchased some liquid sunflower lecithin to try in my chocolate. However, as soon as I tasted a small bit, it went into the trash. I was not going to even try it my chocolate. This is the one I purchased: https://www.mysunflowerlecithin.com/product/all-natural-liquid-sunflower-lecithin/

updated by @thomas-snuggs: 06/07/16 22:27:20

Has anyone tried using sunflower lecithin rather than soy? If so what would be the best option. Would one buy the powder or the liquid. Would the amount added still be the same and what is the ideal amount added. I've read 0.3% as a good amount for the soy version.