The Amazon one is 500 lines/mm, the ebay one 1000, which affects the transmissibility (500 would be brighter), but I think the higher lines provides greater gradation of the spectrum, ergo, more precise. A licensed optical engineer should clarify/correct.
In terms of handling, the 35mm slide ones are easiest to deal with.
The lines/mm also affects the angle to which the spectrum is displayed offset to the perpendicular centerline, need to know that angle so the spectrum is splayed symmetrically on the camera sensor. 1000 lines/mm requires a 34-degree angle, 1200 lines/mm requires 42 degrees, these corresponded to the cheap 35mm plastic grating and the 12mm ground glass grating, respectively. For other lines/mm, refer to this post for the equation and method: