which pot size to use? advice/opinions, please!

[WhiteRabbit]

I went to repot a plant (Onc. alliance, no i.d. - most likely an intergeneric hybrid) - it isn't very large, and was previously potted in an approximately 3 1/2 inch wide x maybe 4, 4 1/2 inch deep pot. It has masses of good roots, some quite long, and they are quite fat! After teasing apart the roots, even a standard 6 inch nursery pot was not big enough to accommodate the roots (and get media in there), without the plant being too high up.

-- So my options seem to be either a 1 gallon pot (6 inches wide, but a couple of inches deeper than the standard 6 inch pot), or a standard 8 inch pot (which is a fair amount wider than the plant itself, tho not too big for the roots). The 1 gallon pot seems to be a decent fit for the roots (a number of the roots are as long as, or nearly as long as the pot is deep), but I generally go with shallower pots for orchids, with the exception of Cyms. I'm leaning towards the 1 gallon pot, but thought I would ask here if others thought differently.

(last pic - there was a tiny, leafless old pbulb that was loose, so I pulled it off - even that had some really long roots!)

Thanks!