We have had both.
A good quality pop-up TC is not that much lighter than a hardside. While there is less rigid hard wall material in a pop-up, that doesn't subtract much weight. Some of the difference is the lack of upper cabinets, but again- not significant.
Looking at Northstar TCs, there is a 300# +/- difference between similar floorplans soft vs. hard.
And we never saw huge MPG differences between the two types.
We did stay in our pop-up at 20 degrees and were comfortable, even without any add-on extra insulation- which is now available from several TC manufacturers.
Some pop-ups have bathrooms usable with the top down.
Others will add their input.