Welcome aboard!
There is no single answer to the question about best kit.
IF the one and only kit for a specific subject is produced by a company which only make half-bad kits then it is by definition the "best" (since it is the only) kit of that subject. If you ask about it you might get the answer to run away from it and build something else.
If there are many manufacturers of kits for a specific subject then we can get into details about that specific subject. The love/hate of individual track links (I love them and hate rubber band tracks but everyone has their own opinion

) can be a critical factor in this type of "beauty contest".
Some kits may be easier to build while others are real pains BUT have better detailing and accuracy.
So, the answer is: Ask about a specific subject and you will get an answer.
Size of 1/35 Chieftain: Almost 10.5 cm wide, the hull is almost 21.5 cm long, the barrel sticks out almost 7 cm behind the hull when the turret is turned to the rear and approximately 9 cm with the gun facing forward. Total length with gun straight ahead is almost 31 cm. Height to top of commanders MG is 8.5 cm.
Measured on the old, and slightly confused, Tamiya kit.
Get one of the Takom kits since they are better. It has indy link tracks so if this is an issue for you you may want to consider another kit.
The best place to get answers about tanks and afv's is in the Armor/AFV forum:
https://armorama.kitmaker.net/modules.php?op=modload&name=SquawkBox&file=index&req=viewforum&forum_id=5&page=1 If you ask about a specific subject in this forum I may decide to move your post to a forum where your chances of getting a good answer are better.
The Modeling in General is mostly for questions like 'Should I assemble or paint first?'.
Asking for the number of links in the track on the right hand side of a Pz IV is definitely over in Armor/AFV and the length of the rotor blades of a helicopter goes to rotary wings.
Most members check more than one forum but the chances of a quick answer are better if the question is asked in the suitable forum.
Cheers / Robin
Edit: and there is a specific forum for posting introductions
https://armorama.kitmaker.net/modules.php?op=modload&name=SquawkBox&file=index&req=viewforum&forum_id=33&page=1/ Robin