Rootstocks are a big factor mostly for soil types/conditions as well as vigor and fruit vs. wood development. Phylloxera resistance mostly comes from the fact that rootstocks aren’t vitis vinifera, but from v. rupestris or v. riparia. If you can do own-rooted, go for it, but there’s a reason grafting is common as Phylloxera wiped out most of the commercial grapevines on the planet.

What kinds of soils are you working with? e.g. clay/loam/sand heavy rocks, and have you done a soil horizon analysis? What are your winemaking objectives and outcomes?