Hello: Direct vent is what I use and have had no problems. It is important to install carefully, to get the venting right. Popularity of power vent may be because they can be installed in more places. With concentric venting, wind pressure basically has no effect on venting ability. I’ve not seen or heard about vent corrosion issues on direct vent heaters. I suspect your plumbers are comfortable with one way of doing things and not another.
On the plus side, direct vent heaters don’t care if the power goes out, they are simpler to maintain, they have complete separation of combustion air from indoor air, likely a little cheaper and they are quiet. Negatives include limited locations for the heater and not as efficient as a condensing power vented water heater,
That’s my take 😎