I've heard of Carrier Infinity going in Mobile/Manufactured Homes with great results. This is just hearsay, but I was told to get MH rating the furnace must include a propane kit standard.
I wasn't comfortable doing that, so I've gone with White and Carrier for my MH installs. I don't sell non-condensing equipment as a personal rule, so both were sealed combustion 90+. I like the Carrier 40,000 as it has the smallest blower and therefore lowest airflow noise.
Love to know if anybody has hard reference material answering these questions...
IMO, if you recommend a package unit it indicates no concern for durable and energy efficient solutions for the homeowner, just selfish interest in selling crap and getting on to the next.