EDIT: I just spent a half-hour going back and forth between a “medium” headjoint and a “soft” headjoint on my Goldie Low D.
Of course there’s no substitute for playing them yourself, and get a feel for what you prefer.
Personally I like both, though they do play differently.
The “soft” has much easier/lighter/more responsive high notes. This is most noticeable on High B, which tends to be the stiffest note on Low Whistles. So without doing any tonguing, you can easily shift octaves like A-a, B-b on the “soft” Goldie.
On the “medium” High A and especially High B require a stronger blow, what I call a “stiffer” 2nd octave.
So on the “soft” Goldie playing things that jump back and forth between High B and low notes is much easier. However the lighter 2nd octave means you have to be more careful when playing in the low octave because it doesn’t take much to flip the notes to the 2nd octave.
Overall to me it feels like the “medium” Goldie is more solid, while the “soft” Goldie feels more spongy.
The low notes on the two whistles are very similar in strength. You can blow Bottom D the same, and when I tried A-cuts on Bottom D they behaved about the same on both whistles.
The tone is different, the “medium” head giving a more foggy musty tone and the “soft” head giving a more pure clean tone.
The air-efficiency is better on the “medium” but it’s not a great difference.
BTW older Goldies were stamped “M” for “medium” etc but newer ones have the actual windway height in mm engraved inside the bell.
This is my understanding, for his Low D whistles:
.8 mm “hard blower”
.87 mm “medium blower”
.97 mm standard “soft blower”
1 mm very soft/easy blower
BTW I’ve not played a V5 so I have no idea how it plays compared to the various Goldie models.