Doesn't matter what you are towing with, doesn't matter what travel trailer you tow. When the combo is close to rated capacities your towing experience is diminished. Mileage drops, towing in wind or up hills can be a struggle, longer trips can leave you feeling drained. Leaving a healthy margin between your trailer weights and your towing capacities gives you a far better experience.
I know this because I've pretty much done all of it. Towed a 3500# trailer with a mini-van. Towed a 5000# trailer with a mid-size 6 cyl SUV. Towed the same trailers with "right sized" tow vehicles. The difference is night and day. It's as simple as that.
And for the folks that tell you that their small SUV towing a large trailer works great, well that may be. My "close the limit" setups towed fine too. But few of those same people have towed with a vehicle that has some margin and have nothing to compare it to.