L*a*b* differences between an i1 and a X-rite SP64 Sphere

I have an i1 Pro and a X-rite SP64 Sphere that we use for taking measurements off of fabric and paper. I have noticed what I consider to be a fairly big difference between the Lab values of the 2 devices, both using the same illuminate (D50/2). What would account for those differences, should I be worried about them, and is there anything I can do to bring them closer into alignment with each other?

I have not had the opportunity to play with a spherical spectrophotometer, but what I know from profiling fabrics is that an i1Pro will tend to return measurements that are too light off of uneven surfaces. The illuminant seems to bounce off the fabric at different angles, and this confuses the sensor.

The purpose of the spherical device is to collect the light inside of an internal spherical cavity. I would imagine that light does not scatter quite so much this way and the measurements are more accurate.

I’m not sure you can get an i1Pro to do the same thing. We use SpectroScan tables to measure fabrics and matte paper targets here, because we can add a polarizing filter which seems to cut down on stray light entering the measurement head.