Though Choice
This is a difficult decision. Both are designers I aspire to wear but for different reasons.
When I think of Gucci, I think of two different styles. The first is the overworn GG print items that I believe are for people with no imagination that have to shout that they have a designer label. The second is bright colours that clash and beautiful shapes. The spring/summer 2007 collection demonstrated this wonderfully with neon clashing paisley maxi dresses amongst other items. This was copied all over the high street. Spring/Summer 08 saw the american style star prints which again can already be seen recreated all over the high street.
When I think of Prada I think of sleek, clean modern lines and futuristic shapes. The problem is that nothing recent comes to mind. I remember their cream funnel neck winter coat from about 5 years ago and their signature red prada label. So on that basis it would have to be Gucci for memorability.