Probably depends about the coverage in your area which is difficult to know until you start using a phone on that contract. I was on giffgaff for a while but found their service a bit hit and miss. I now have a 12 month sim only contract and an s4 which is excellent. Unlimited calls texts and really fast Internet including 4G for 15 quid a month. 3 have also announced you can now go to countries like Italy, France, the USA and Australia and use your phone as if you were in the UK which is frankly phenomenal value compared to a few years ago.