reply to riahc3
They are all pretty much the same as Telefonica owns all the lines so they basically control all the other companies. The only other option, if you happen to live in a major city, is ONO which has its own fibre-optic cables and thus can offer faster speeds.
Apart from that there are WiMax services such as IberBanda which is good but more expensive (but doesn't need a phone line) or connect via the mobile phone network using a usb dongle (good if you don't use the internet much but it is capped pretty low if you download a lot).
Hope that helps!