The i7 4500U only runs at 1.8Ghz and has a 6MB cache. The i7 4700MU is much faster running at 2.4ghz and a turbo of 3.4ghz with a full 8mb cache and 8 threads.
The 4700 also supports up to 32gb of ram compared to the 16 the 4500 offers and has better pci express support.
The i7 4500U only runs at 1.8Ghz and has a 6MB cache. The i7 4700MU is much faster running at 2.4ghz and a turbo of 3.4ghz with a full 8mb cache and 8 threads.
The 4700 also supports up to 32gb of ram compared to the 16 the 4500 offers and has better pci express support.