I just brought a 4500u laptop for my son for school and a bit of light gaming on the side and after having a play with it myself I have to say I'm really impressed, feels very snappy and scores 2300 in cinebench R20 which is just shy of a desktop 7700k while only using 25w.
In regards to the 4700u being worth it over the 4500u then it depends what type of workloads you're planning on doing.