[Q] After I-526 petition, is it better to do IV processing or I-485?
It really depends on many facts, and the ability of the investor and family members to physically remain in the U.S. for many months.
Normally, we would say do IV processing, unless there is some urgent need to emigrate to the U.S. quickly, or the Investor and family members are already physically staying in the U.S. on nonimmigrant visa status.
The important thing is you have to indicate whether the investor will do IV processing or do I-485 processing on the I-526 form itself. Therefore, this is something you have to think and decide in advance.