Google versus Yahoo on GPS visualizer

I just started doing POI's and used Yahoo on GPSV and it sent me a 1/2 mile away from the actual destination. I reloaded it using Google and had my GPS show me the map and it was dead on.

Here's the weird thing.
I redid 2 of my uploads using google and looked at my closest costco to check to see if it was correct and it was 2 miles off. I checked the Yahoo coordinates and they were dead on.

Now I don't know which one is right and I'm gun shy to upload POI files that may take someone way off course.

Is anyone else having these issues?