That is not the right question to ask. Different architectures can make a big difference at similar clock speeds. Clock speed is just one of a lot of factors to consider when appraising a graphics card's merits. More specifically, it is better to match up two cards and see what the differences are. Here's Tom's Hierarchy chart which makes life easier for most of us:http://www.tomshardware.com/reviews/gaming-performance-radeon-geforce,3018-7.html
Here with a quick glance you can see the relative strength of video cards by model numbers. Models with M or Go designation are mobile variants (laptop).