I'd say you have to look at the tradeoff between convenience and security. Whatever you do to secure your bike there's always a chance it could be stolen. A bigger heavier lock would be less convenient and more expensive, but then you would have more security as it could go round the frame as well as the wheel. However someone could still cut through that lock with powertools, so there still a chance it will be stolen, and for a sufficiently valuable bike even that might be worthwhile for a thief.
So it depends how bad the crime is in the area you are leaving it, how long you are leaving it for and what the value of the bike it amongst other things. You have to make stealing your bike a less attractive proposition to a theif than some other bike.
for a bike worth less than a couple of hundred quid and that doesn't look new its probably sufficient if you are leaving it for a short period of time on a busy street say. Even then though the front wheel and saddle could be exposed.
So it depends how bad the crime is in the area you are leaving it, how long you are leaving it for and what the value of the bike it amongst other things. You have to make stealing your bike a less attractive proposition to a theif than some other bike.
for a bike worth less than a couple of hundred quid and that doesn't look new its probably sufficient if you are leaving it for a short period of time on a busy street say. Even then though the front wheel and saddle could be exposed.