cheap vs expensive flexplate

Well, the B&M Flexplates are definitely what I'd call Tank-Armor Material. That being whatever you throw at it, it's just going to laugh at you and wait for more abuse. :D A very stout piece of equipment.

The Stock flexplates have no kind of balance to them, they're neutral, you can run it behind any mopar with the same bolt pattern on the crank. If you've got a Neutral Balance Torque Converter (most aftermarket converters are neutral balance, stock converters for the 360 and certain other engines have weights welded to them), then your only choices are to buy a 360 to Neutral Balance B&M Flexplate or buy a Weight Kit and weld them to your torque converter in the correct places.