A russells Lion stays smaller than the volitan, it gets 10-12 inches, where the Volitan gets 12-15 inches.
I took this from the Info sheet:
Russell's lions are one of the more commonly available lionfish in the hobby, and are frequently misidentified as "red Volitans". Juvenile Russell's lions have a whitish body with dark brown vertical stripes. The pectoral fins are pale white with light brown and blue spotting. As the animal grows and ages, the body pattern becomes more diffuse and turns rust-brownish in color, while the pectoral fins turn darker and lose the spotting. The second dorsal, anal, and caudal fins are clear with an occasional brown spot.