"Can I ask, Why a bunjin-type pot ? Because of the informal style, or the height of the tree ?"
I saw the tree as "bunjin-ish"
for lack of a better term.
Its trunk, especially the lazy irregular curves in the bottom third of that thinnish trunk, imply a loose, rustic, relaxed quality that should be echoed in the pot.
The branching is a bit denser than a typical bunjin, but that's fine. The informal rustic feel the trunk is a little between informal upright and bunjin.
A deeper oval with strict contours or bands, or worse, a rectangle pot with right angles, would work against that nice trunk by putting a formal frame around it.
I'd avoid a starkly unglazed pot, even if the pot was a bunjin pot, with this tree too. The trunk looks very much "alive" and a darker somber pot would tend to deaden that feeling. The goldish, warmer tones in the Dale pots would complement the spark that the lower trunk brings.