Nexus 5 is the best so far, However OnePlus have just released a new smartphone called OnePlus One. It's going to be £229 for 16GB and £269 for 64 GB (yes 64 GB). It has even better specs than the Nexus 5. It's supposedly going to release soon, currently it's invite only. So you could wait a couple of months to see if it comes out. It's an insane deal. Although it is quite big (5.5inch).