You will face double the latency if you choose US, l have some serious issues with latency between one of our private 10G links WAN links and there is nothing we can do about and its a point to point link.
The link is between EU and Houston!
Since Econet/Liquid Telecoms have POP and Linx(London Internet Exchange), chances are that if your traffic goes via Econet, there is minimum latency compared to PowerTel which route its traffic via Bots