There are three or four versions of the Bulldog. An extra-long model, a long model, a mini-model, and the lighter "TC" version. All of them should perform at the soldsecure.com "silver" level, IF (and ONLY IF) they are correctly used.
OnGuard rates it locks (5 stars, 4 stars, 3 stars) by their weight class and price class, with the Brute models being the most expensive and heavy, the Pitbull being in the middle, and the Bulldog being the less expensive light lock. ALL of them will stop the typical prying or leverage attack when correctly installed.
For a u-lock, especially a lighter u-lock, to be effective, the "U" portion of the lock must be filled, leaving no room for prying tools and leverage tools. Use the smallest version of the Bulldog that will fit around your rear wheel (just behind the seat tube) and around a thick, beefy steel post that is securely set in concrete.
The editors of "Cycling Plus" found that the Bulldog was as tough against prying and leverage attacks as the most expensive locks WHEN used correctly.
The "extra-long" versions assume that the bike owner is removing the front wheel and enclosing it in the lock. I would prefer to use the SMALLEST Bulldog, using one around the rear wheel, and one attaching the front wheel to the frame.
The Bulldogs are as good as any bike lock in the world that weighs just two or three pounds WHEN correctly used. To have a higher level of security, you need a lock rated "gold" by soldsecure.com. "Gold" rated locks weigh from five pounds to eight pounds. Light weight is why the Bulldog is a lock I use for daytime use in a good neighborhood.