Congrats on your plans! Moving into an RV (or travel trailer) is a huge step.
As far as retaining value travel trailers definitely are depreciating much slower than motorhomes. But regardless of which you choose to buy my advice would be to avoid buying brand new. Any new RV automatically loses 25% of its value the moment you drive it off the lot. At least here in the States. Try to buy gently used. Ask if anyone lived in it full-time, had pets in it, or smoked (that you can do by both asking and observing the seller). All of the above aspects will affect your enjoying your new home on wheels one way or the other. Don't worry about the looks of the interior too much: I've seen people do a marvelous job painting walls, reupholstering seats, and sometimes ripping off the carpets and replacing them with hardwood flooring. If you are handy you can buy your first home cheap and then turn it into a real gem. Granted resources are also available.
I agree with your parents saying that it is easier to take care of a travel trailer. You can also use your tow vehicle to go around explore after you check into a park. But when it comes to things break, it happens to both motorhome or a trailer equally - imagine your home going through a series of earthquakes (that's what it looks like every time you move around). Of course things will get loose, you will be spending some time fixing things around. That is true to both tt or a motorhome.
In the end think about your lifestyle and your level of necessary comfort. Motorhome fits ours: we have a bunch of remote controlled airplanes, 2 scooters, 2 bicycles, a paddleboard and a raft. All those toys we tow with our house on wheels. It is just seems to work out better for us. I would suggest for you to think of you needs for recreation. If you don't need much, maybe you can even try out to convert a van (I've seen really interesting ideas on the web) and go explore while young. You can always upgrade later. :)
Good luck!!