I've had both. Popup is less maintenance without a doubt. Its easier to tow and overall less of a investment. Its possible to store a popup in a regular garage, perhaps why some older units are in such good shape.
Travel trailer is without a doubt nicer when traveling. There is so much more floor space. The 3x4' floor area of a popup gets covered in shoes and coolers quick! A TT is so much quieter inside that you can sleep regardless of what is happening outside (noisy campers, rain, etc.). And packing a TT is so much easier then popup.
There really isn't any comparison. But, I will say that the popup was less maintenance and could be towed with anything.