TeaDB did
a video recently on teaware and linked to an
article by MarshallN which talks about this to a degree. I found it to be a very interesting read and it's written by someone who owns a lot of teapots.
I'm not sure what people on here will agree (or disagree) with; but what you're asking could be answered simply (does it brew good tea?) or more intricately.
For me I largely agree with MarshallN's points. Lid fit isn't terribly important (within reason, it shouldn't fall off). Dripping is only really important when you're pouring for others etc. etc. I can live with a lot of things if it brews tea well.
I mainly look for factors that will help my brew, tailored to particular tea - so primarily:
- what is the pour speed (NB: accounting for correct viscosity of liquid for the tea I'm going to be brewing)?
- What is it made from? How thick or porous is it (if it's clay)? Is it good clay or bad clay (see MarshallN article)? That will effect the heat retention and heat loss. If it's an oolong you'll want something like a thin Zhuni as it gets very hot but it cools quickly (and that helps with retaining scent).
- What shape is it? Shape is a key factor in design of any functional object. Can you fit your tea in easily? How will the leaves unfurl if it's a balled oolong or rolled yancha? Some people like using a tall pot for dian-hong. Or a flatter/rounder pot for puerh.
Some tea will need almost 'flash' steeping (in which case you might not want to use a pot anyway) a cheap gaiwan might do a better job. Other tea will be okay with a 10+ second pour. In general, like Bok said - faster pour is usually better.
You can see why people might use different pots for different tea. So, what tea do you want to make?
There is a lot of theory on
clays that perceptibly alter the taste of a tea, so people will use Duan'ni for sharper stuff that they want to round off (young sheng) or Zhu'ni for very aromatic (oolongs etc). Myself, I'm not sure I believe it - but I'll keep experimenting.
'Does it brew a good pot of tea?' - is a much simpler way of saying all this. That it isn't going to poison you over time is definitely a nice plus.