I've had shellac and the Jessica equivalent. They are good, and because they are gels they let your nails breathe. My nails grow quite quickly so I need to replace them every two weeks, but a friend of mine managed to keep them on for a month. You can take them off if you have an acetone varnish remover. I usually just pick them off as they lift, but that's no good for your nails!!!
I had a shellac a week before my wedding and it had chipped before the actual wedding. Acetone didn't even touch it, so I ended up chipping it all off and then having to paint my own nails (I am really bad at this, which is why I'd opted to pay to have it done properly!)
Also, I didn't like that it felt so raised, and couldn't go right to the cuticle - I ended up with a gap between the shellac and the cuticle.
I wouldn't have one again, thought it was a colossal waste of time and money tbh.
I've had shellac and also a paint on gel nail. The shellac was more like normal nail varnish so looked thinner on. They both lasted about a week and a half but by then the gel nails were lifting by my cuticles. Neither of them did any damage to my nails, neither of them chipped. I would definitely get the shellac again, ask them to really make sure they deal with your cuticles properly so that there is less chance of them lifting from that end.
I had the gel nails soaked off in a salon but took the shellac off myself at home with acetone nail polish remover.
I liked the colours for both but it's all down to preference. There was definitely more colour choice with the gel nails but that could be down to it being different salons.
I had a Gelish one, which was excellent. Lasted two weeks with absolutely no chipping. It started to lift at the cuticle then on a couple of nails. My nails were actually in much better condition once it was off.
You can take it off at home. Soak cotton pads in acetone nail polish remover. Wrap them tightly around your nail tips with tin foil for ten minutes, then gently scrape off with a wooden or plastic orange stick. There's youtube video's if you want to have a look.