An acquaintance of mine bought (several years ago, before the fixed thing became quite as popular) a 'cheap' bike from one of the scallies in the Brick Lane Massive. The kid told him that the small, strong d-locks were the hardest to get through because you needed those hydraulic cutters the fire brigade use (which they nick from time to time...), because there wasn't enough room to get a jack in and normal bolt cutters were useless. Anything with a chain they could get through in no time.
So on the basis of that, I do think what lock you use makes a difference. Yeah, they can get through all of them eventually - especially if you lock your bike to something that's weaker than the lock! - but given that trawling London with bolt cutters discretely is difficult, they tend to go with what they know they can get at quickly.
An acquaintance of mine bought (several years ago, before the fixed thing became quite as popular) a 'cheap' bike from one of the scallies in the Brick Lane Massive. The kid told him that the small, strong d-locks were the hardest to get through because you needed those hydraulic cutters the fire brigade use (which they nick from time to time...), because there wasn't enough room to get a jack in and normal bolt cutters were useless. Anything with a chain they could get through in no time.
So on the basis of that, I do think what lock you use makes a difference. Yeah, they can get through all of them eventually - especially if you lock your bike to something that's weaker than the lock! - but given that trawling London with bolt cutters discretely is difficult, they tend to go with what they know they can get at quickly.