It all boils down to a certain number of watts used giving the same heat output per watt, minus whatever small amount is consumed by a fan, if there is one. The differences are whether one wants a big surface area that's very warm at, say 1500 watts vs. a small hot area at 1500 watts, and various combinations of convection vs. radiant heat, or fan forced heat.
If one likes the quick heating and the feel of forced air heating and keeping air temperatures fairly uniform at both your head and your feet, and if one finds one that doesn't sound like a hair dryer (I haven't owned a Vornado but will keep them in mind), then they'd be a good choice if not too bulky and if they seem like they could be safely packed away for travel.
I like the silent operation of oil-filled units but don't know how well they'd pack or travel. Their mostly-convection heat is silent and comfortable despite some potential for more stratified air than with a fan forced unit, and it can take a while to warm up a room. These, and the "micathermic" (also silent), have large surface areas that get very warm, but not hot enough to quickly burn. Micathermic also give off a bit more directional, radiant heat, along with the same convection heat as an oil-filled unit. I don't know how well these would travel, either, but the lack of moving parts and of fluid would seem advantageous. Micathermic can be wall-mounted, getting them out from underfoot IF one can find a spot where they won't still bang into it.
Similar in material to micathermic but in a smaller, more portable size is the ceramic heater. The smaller size would mean it'd have to be a hotter surface if consuming the same watts, but the otherwise higher surface heat is instead mitigated by a small, usually quiet fan. Many are no larger than a large shoebox, so easy to place on a counter or out-of-the way corner as they heat with a combination of weakly fan-forced, some convection, and a little radiant heat.
Finally, various radiant heaters (quartz has been common) are the other option. They feel good as they quickly warm the surface (you) they're pointed at, and like an outdoor patio heater, are unaffected by drafts. But, their surfaces do get hot so I'm not sure it could be placed where it's do anyone any good and not be a trip or burn hazard. I don't know how well they'd travel.
As there have been numerous recalls on different makes and models of all classes of these heaters, do research on that (Consumer Product Safety Commission is a start), read other reviews, (unbiased Consumer Reports is always worth checking) and remember that travel in an RV, even if in the often nicely packed shipping boxes they come in, may be tougher on them than the typical home use they were intended for.
We've owned all of these at one time or another, and I sold all types (and took returns) available in the early '80's while working big box hardware retail while in college. Each has their place.
I do recall an outfit renting VW Vanagons to mostly European tourists would also sell or rent (can't recall) them small ceramic heaters for about $20-30. Given the desire for happy customers and potential liability issues, that may say something about those heaters for RVers.
