Try each of them in small batch blends. "Thin Leaf" is probably from the very bottom of the plant, and would be called volado, if it were cigar leaf.
My experience with flue-curing has given me the impression that the very first priming (the very bottom leaf) comes out thinner and lighter colored, and has a more floral aroma than the lug leaf (just above the bottom leaf), but has less sugar than the lugs. My first primings of the VA Bright Leaf variety flue-cure to a pale, canary yellow; the next priming is more lemon yellow; next up is a marigold, with a heavier, richer flavor, and more nicotine; my top leaf tends strongly toward the brown end of the spectrum, and has the fullest flavor and nicotine.
[Just as a historical note, the term, "bright tobacco", emerged in the middle of the 19th century to distinguish air-cured leaf from flue-cured leaf. It encompassed many varieties that were routinely flue-cured, following the spread of the technology of flue-curing. Southeastern Virginia and northeastern North Carolina were labeled the Bright Belt. So, the NE North Carolina Bright Belt grows "Virginia" tobacco.
Flue-curing itself is just a curing technique, which can be applied to every variety of tobacco. Some turn out crummy when flue-cured, like burley and most cigar varieties. Those varieties that were recognized to be marketable as bright tobacco after they were flue-cured were eventually designated by the USDA as being members of the (entirely fictitious) "class", FLUE-CURED. It's like calling a particular cut of beef, "grilled".
Sorry to drone on about this, but the notion of "class" and the term, "bright", continually lead to a lot of confusion, since they seem canonical, rather than just being, in reality, USDA marketeering. But we're stuck with them.]
Bob