RKC02, I don't know any more about the difference other than suction cups vs magnets. I would agree that maybe a magna shade would be easier to install, however the Prompt is not that difficult and can be done from the ground. I carry a ladder so i use it and it makes the install very easy.
I'm don't think the suction cups will leave a mark or not. What I can tell you is at my summer place I have had the screen on for about 2 months and removed it earlier this week to wash the coach and windshield and it hadn't left any mark. Also no holes are required.
Also understand that the cups have a life span of about 1 - 2 years so they have to be replaced at some point depending on how severe the sun issue is. The good thing is they are easy to replace and cheap at about $1 each if you order extras when ordering your shade. I think you can also buy them at Home Depot or Lowe's. They are your standard 3" suction cup.
From all I've heard MagnaShade is a top quality product with a lot of satisfied customers.
Let me add that I'm also very happy with my Prompt RV shades. I found out about them from another camper who got his Prompt RV shades at the Tampa RV show this past January. He was really happy and convinced me that they were the way to go.
Marc & Jan
Molly, Abby & Katie | The Cocker K-9 Kids!|Toad 2014 Cadillac SRX
2012 Berkshire 360FWS, Brake Buddy Vantage|Wineguard Travler SK-3005