I have an iPhone 6S and an iPad Mini 2. If the iPad Air 3 has Pencil support, I'll buy it plus a pencil the first day! Full Stop.
Regarding whether the IPP being "best"? Nope. Not by a mile. In. My. Opinion. It is WAY too big. It won't won't fit in my current computer case and I don't want the extra weight. And it's very difficult to hold unless you have huge hands (I don't). IMO.
Conversely the iPad Air 3 is just right in both size and weight. It's far more usable in way more situations. IN MY OPINION.
Terms like "best", "worst", "bad", and "good" are just opinions and are definitely NOT facts. Opinions are related to your needs, wants, constraints, and pocketbook, and how well a specific product meets those.
For those people in this forum who think their opinion is the rule of law, then my message is, "Grow Up". Do not EVER presume that you have the capacity to understand my needs, wants, constraints, and pocketbook. Likewise I will never presume to define your needs, wants, constraints, and pocketbook because I don't have that capacity either. I can't see through your eyes and you can't see through mine.
Please... Argue facts or label your opinions as opinion, and never get them mixed up. Doing so runs the risk of pi$$ing people off and making them lose all respect for you. And yes, this is my opinion.
Dan.