David & Jo Ann,
The Vantage was only manufactured for about 1.5 yrs [mid-2012 thru 2013, I think?], and there's very little online info or details available. There are a few Vantage owner/members here,
and hopefully they'll chime-in with some specific answers for you. You could also do a forum search & might find some useful info.
You asked about exterior storage -- on the floorplans, (see flyer/links below) exterior storage areas are indicated by a "black arrow"... only 1 arrow (total) per model & only on the larger trailers. Apparently there's very little exterior storage & no pass-thru. As for your *unknown destinations* and possible northern winter's & below freezing temps...??... IMHO, probably not a good idea.
Very few construction details in the flyer, but this line/brand was likely intended for spring/summer/fall vacations & camping trips, not (extreme) winter weather use.
MH vs TT... you're correct, a travel trailer might be "happier" being parked for longer stay's, but be aware that a trailer (regardless of brand) will need some added winter precautions & preparation (wind block/under-pinning, etc) if parked long-term in winter extremes. There are a select few (high-end) 5th wheels & travel trailers which are probably better suited for hot/cold, but, the greater majority (industry-wide) are not designed/constructed for extreme weather use. Unfortunately, none of those high-end brands are shaped like an Airstream.
Trailer Life Review [& public comments]
to the forum, and hope this helps,
Terri, the Chevy co-pilot