Kabinett, Spatlese, and Auslese can mean sweetness in the final product, but usually, they mean the ripeness of the grapes at harvest time. German law states different levels of ripeness get different titles. Therefore in Rieslings, Kabinett was the least ripe, Spatlese was more ripe, and Auslese was quite ripe. After that, we get into desert wine territory with Beerenauslese and Beerentrockenauslese. Finally, you end up with eiswein.
Wines from the Peisporter region tend to be always on the Spatlese and Auslese type. Usually, most piesporters rate in at either 1 or 2, and are perceived to taste sweeter the more age they get.
Get a good pieseporter that you like and before you drink it, measure what the SG is. A "1" should be between 1.004 and 1.007. A "2" is going to be between 1.008 and 1.011. A "0" is usually below 1.003. The reason why we get well below 1.000 is that we don't usually get a lot of residual solids left in the wine as we don't use whole grapes, but concentrates in kits.
Anyways, I always advocate getting the biggest and best kit you can afford, so I'd go for the bigger kit, however, if the VR is a closer match to your tastes, taste rules all!