As always, a modeller who asks for "best" doesn't define what attributes are important to him. Best could include:
1) fidelity to prototype in detail
2) robust construction
3) quality and accurate paint scheme
4) metal wheelsets of semi scale size
5) mounts for Kadee couplers
6) value for money
As you can see from the replies to the thread, different folks have different priorities on what is valuable to them.
All of this overlooks the fact that in terms of modern (cars currently in routine revenue operation on the prototype), there is a very limited choice. In 1:29 there is but a single tank (USAT), a single hopper (Aristo), one covered hopper (USAT), 2 intermodal cars (Aristo, USAT) and a single boxcar (Aristo) ... other diesel era cars are of prototypes now at least 50 yrs old and they are obsoleted for routine service. There are no flats or gons and no specialty cars at all (like autoracks for example or newsprint cars or cylindrical covered hoppers). The rolling stock situation is not so much a question of what is best but rather what do you want and then buying from the only game in town if there even is one.
Regards ... Doug