Runkeeper on iPhone 4S v Garmin 205

I have been using Runkeeper on my iphone 4S along with my Garmin 205 and I have found that the 205 by the end of a 7 mile run was 200m short compared to the Runkeeper.  Therefore Im not sure which is accurate ?!?! any advice anyone - thankyou !

As Dave says.

less than 2% out

I have just ditched my iphone 4s with runkeeper app in favour of a garmin 305. I haven't used them together yet but will make a point of it for comparison purposes.

What I did notice when using runkeeper was that the mile splits could vary by 50m or so when running running identical routes. For example a 6 mile out & back route I use for my tempo run - the turn point at 3 miles was never the same and could vary by + or - 100m even tho the start point of the run was always exactly the same.

I think the garmin updates position from the satellite much more frequently than the GPS used in runkeeper so for that reason I would guess must be more accurate?

Neither is completely accurate but the Garmin is likely to be closer and more consistent. Plus if you are concerned about accuracy you are likely to want to refer to pace, etc while you are running and the wrist-mounted device is much more convenient for that IMO