I think there is a difference in getting an extended coverage for a MH compared to a TT... Lots more to go wrong on a MH with just the drive train alone...
Most folks seem to get the ext coverage for their tow vehicles, so that makes sense too.. (I didn't get any extra coverage over the base factory coverage on my 13 F150 however).
It's purely a matter of "piece of mind" thing for sure... That's why I mentioned the whole "if it keeps you up at night" either way, that's when you need to do what you have to do to sleep at night! ;)
Mitch