Duel feed/Single feed?

Some help please, i am hearing conflicting reports about a single feed and duel feed, i am looking to get a honda GX390 21ltrs a min at 200 bar pressure washer, some sellers are saying single feed is okay and there are others saying it needs a duel feed, i generally try to get advice from people that use the machines rather than people just selling them, so any advice would be great.

My machine matches your spec and has dual feed, never have any problems with it.

Always go higher spec when possible and can afford it, can it hurt?