As they're now the same price, you would be better off buying the Sony KDL40WE663BU, yes.
The spec sheet is identical, bar the WiFi, Smart features and Screen Mirroring (content and apps from a compatible smartphone to the TV). Which considering the £30 RRP increase, sounds about right.
The top end model (WE753) adds their TRILUMINOS tech and increases the screen size by 3 inches. Probably not worth the £100 extra though, because then the price is in 4K territory.
In terms of 4K though I would seriously consider checking out the Samsung UE40MU6100 with 5 year guarantee:
https://www.johnlewis.com/samsung-ue40m ... k/p3215451, and reviewed here:
http://www.rtings.com/tv/reviews/samsung/mu6300. It's simply got a different product code in the UK to the USA. In terms of input lag for gaming it's one of the best TVs of 2017 and Samsung's current best performer (20.2ms).