Basically, they both ruin your nails but acrylic can be soaked off with acetone and so are a slightly better choice. Saying that, your original nails will be softer and weaker from the filing prior to application and break off anyway. You're probably better off buying a nail protecting serum or product such as Sall Hanson's Teflon nails which I've always found to work providing you use it regularly.
i have had both - personally i prefered the gel nails, and my own nails grew well nderneath them so that when they came off i was able to just have my real nails showing, although they were ridgey for a bit untill the bit where thyd been stuck on grew out