I've been playing around with both sites, have both apps and I prefer Spark People over MFP. Reasons being, in my opinion, MFP only lets you track nutrition and exercise. While SP lets you do so much more, add extra goals, there are articles and videos to help you stay informed... several things!
My personal draw back to SP is the scan tool for tracking nutrition. I scan an item and then have to choose from others entries. With MFP the scan tool enters the nutritional info for the item scanned, very helpful.
My question is how can I use both apps without it being duplicated, time consuming, complicated and frustrating? I feel I can track nutrition more conveniently with MFP but want to track everything else on SP and enjoy the site!