So it seems that there's not a vast difference between stiff vs liquid starters if we're comparing it's usage for home bakers like myself.
However, from experimentation, there's subtle differences in the way that you feed, store and refeed the starters that have yield different results in the final baked product.
Stiff starters, also known as pasta madre (italian for mother dough) is typically used in panettone. Due to the richness of panettone, isn't isn't easy for gluten development in a rich mixture as compared to plain sourdough bread (as noted when trying to make sourdough brioche/cookies vs bread etc).
The obvious differences between stiff vs liquid starters in the final product.
- can generally be keep longer in the fridge if wrapped (doesn't develop hooch/grey skin)
- due to the lower hydration of the starter, dough shaping is a bit easier/more forgiving
- has a more sour taste (Edit: Taste may be related to feeding routine/build-up of lactic acid bacteria. credit: @Reverent Lapwing)
- use in rich doughs, bread loaf pan (develops tight texture, very enjoyable to eat)
- need to kept in an airtight container to prevent hooch (you'll still have it, but its less dominant than compared to a loose sealed container).
- turns grey within 5-7 days, which should still be usable
- haven't found it as sour compared to stiff starters
- need to be precise with water hydration (I tend to get more liquid doughs)
Recommendations: use for sourdough, wholewheat etc