You ought to know this stuff!
A candela (or candlepower) is a measure of light SOURCE output. A lumen is a measure of light intensity at an object or point.
A given light source might make a lot of candleas but depending on how diffuse it is (scatter) or what's in between the source and destination (like a dirty lens or whatever) the lumens may be significantly lower.
LEDs tend to be directional so I'd expect little loss between the source (candlepower) and the destination object (lumens). They do tend to have very poor off-center illumination though due to how naturally directional they are - they require reflectors/diffusers to scatter the light.
From a practical standpoint, what you're really concerned about is lumens, almost never candlepower.