Not sure exactly what you mean by Europe IP or USA IP. I'm guessing you mean IP service (or dedicated server) from Europe or USA. An IP address can be registered to an American company and be located anywhere in the world.
As far as service, if most of your users are in Spain, then I would get a host in Spain since network latency will be minimized. If the site is hosted in the US say on the US east coast, you may be looking at 50-100ms latency just to cover the distance to Spain.