I would prefer tiny kyusu above everything else. Kyusu size of ~100ml are simply amazing. But if only from two items in topic, i guess it would be shiboridashi, i don't own one yet. Hope i can fix this soon
I agree with you.
However, i prefer think sharp and material (and volume of course).
For very high grade teas that we brew with few water, lots of leaves, Something large and flat seems to be better, and almost shiboridashi are like this. But for the same high grade teas, we usually want to bring out sweetness/Unami, and for this porcelain works better. Porcelain hohin are more common than porcelain shiboridashi i think. Of course, this is only general speaking. (there were research last years that's shown ceramic make tea taste stronger, bringing out the tea's Umami and astringency, porcelain get a lighter taste with no astringency).
Finally, accessories is more for me a question of mood.
Besides, in a lot of wholeseller catalog, shiboridashi is a subcategory of hobin.