The Pearl is simply a 73 degree angle road stem where the Jaguar is a drop-angle stem for track. Other than that, it's hard to tell them apart. If anything, the finish is a bit better on the Pearl. No NJS stamp on the Pearl of course, but that isn't relevant.
Jaguars only come in 25.4 mm clamp size. Pearls come in 25.4 and in 26.0, but I've heard that only the 26.0 is imported into the US. That makes the Nitto shim very useful since it's designed to let you put a 25.4 Nitto track bar into a 26.0 Pearl stem -- and it actually fits the width of the stem nicely.
Pearls are very nice stems. There's no reason not to consider one. They are not a lower grade of stem.
One thing: Pearls seem to run about a centimeter longer than their listed size. Be sure and actually measure it and don't just trust what the stamping on the stem says.