i vent both middle d and high d, though i tend to search for alternative figurings all the time as they each have their own qualities, tonally and such but i use all varities of fingerings and tailor them to the tune of interest.
oxxxxx middle d
oxxooo high d
i play a pratten style. to me the vent d is more accurate tonally, and you can push hard on it and make it bark, howl or to an extent overblow and it’s still pretty solid.
the best thing about venting the middel d is it sets you up to roll, cran, squiggle the middle d. take a finger off and oxxoxx and you’ve got a sorta cnat, take another off oxxoox and it’s a bit different. on the oxxoxx use the lower x to wave or vibrato the note. if you hold the vented d and move fingers in rapid succession, in a statactoo or closed type piping approach, you’ll been to get that middle d roll with cnat which can be quite fun, yet over done, but it sets you up for other stuff too.
the high d
oxxooo is also an alternative fingering and the xxxxxx can be overblown to acheive the same note. however, to me the oxxooo is much more pure and focused tonally. in addition oxxooo leads to oxxxoo C# and another alternative Cnat oxxxxo which is also a wonderful high Cnat in comparison to half holing the high |ooooo which is always the best approach, half holing is where the music lies to my ear, in general.
you can also “squiggle” with oxxxxo and it’s alternatives for interesting effects.
have fun