Pros and cons both ways. I'm on favor of the pop up going down the road. Had a hardside Lance and my truck is similar to yours but lots older. The pop up is like having nothing in the bed at all, especially in the wind or passing trucks plus I like mine because it fits in the garage when not in use.
Hardsides 'feel' more secure when you are inside and with a hardside there is more storage and appliances can be mounted higher.
Pop ups have light years better ventilation, I didn't even get ac (and option) on mine, no need.
Pop up's will be lighter apples to apples as well.
Finally is the overall height issue. With a pop up, clearance is never an issue and because I run off road a lot, a pop up with it's low stowed height and lower Cg is a much better option for the wife and I.
Your mileage may vary however. They aren't for everyone.
2015 Backpack SS1500
1997 Ford 7.3 OBS 4x4 CC LB