How does REITS doing a private placement/preferential offering affect retail shareholders aside from share dilution?

Private placements definitely dilute the retail holders but at least retailers don't have to cough out the money. It is also more efficient for the company because it is faster. Sometimes a major deal needs to be closed quickly or they can find someone else.

There is alot of admin fees and expenses to do a public rights issue. So, they also saved on cost savings.

Preferential offering is slightly different. It is open to existing holders, not just big instituitions. So it allows loyal shareholders to participate and subscribe at a discount.