This is also my experience. I bought portable panels at first to avoid drilling and mounting to the roof. Now I love them because I camp in the shade whenever possible.
But I also stealth camp around town fairly often, or in areas I don't really trust leaving the panels out. But I need to charge the battery
...For this reason I'm convinced that I want roof-mounted panels in addition to my portable panel. Both would be really, really nice. If I had to only have one type...for my personal type of trailer use, I guess the portable are more adaptable to different situations. I've left my camper in the work parking lot for a few days when I was out in the field, and used a ladder to haul the panels to the roof and left them there while I was gone, laying flat. A pain, but workable. Much less chance of theft, and still a good charged battery
when I got back.
But both is definitely the best option.
The portable panels can be a pain. I bought a package which included folding panels (90w), a few different battery-connection choices and an aluminum case. The case really helps. The photo shows how I transport it. Silver case on the left. Between getting the case out, pulling out the panel and standing it up, then putting the case back in my truck 15 minutes would be the absolute max. Probably not more than 5 if I'm motivated. I have a ratchet strap holding the case in place.
Luckily there's not much theft where I live. It only takes once...but so far I've had good luck leaving the panel sitting out while I'm gone during the day. No lock.
It's heavy and it takes up space and a little time, but it's the only way I have to charge my battery
so it's just part of setting up camp.
When I save the money, though, roof-mount panels are definitely happening.