Belt drive or direct drive — the honest tradeoff
There is a real answer here, and it depends entirely on how much you run the machine.
The mechanical difference
Direct drive couples the pump straight to the engine, so the pump turns at engine speed. Belt drive gears it down, so the pump turns slower and runs cooler.
Slower and cooler means longer life. That is the entire argument, and it is a good one.
Where the line falls
If the machine runs a few hours a week, direct drive is the sensible purchase. It is cheaper, it is more compact, and you will not wear it out.
If it runs most of most days, belt drive pays for itself — not in the first year, but well within the life of the machine. Pumps are the expensive part and heat is what kills them.
The part nobody mentions
Belt drive machines are physically larger and heavier, and belts are a wear item that needs occasional attention. That is a genuine tradeoff on a tight rig layout, not a footnote.