Best D-Lock for around £20- 25

captc

I have been looking on Amazon, and they seem to have some good value D locks around the £20 mark, including the extra cable.

These are the ones I've looked at:

Master Lock Street Fortum (Gold Secure) £21.49
http://www.amazon.co.uk/Master-Lock-Street-280x110mm-1200x10mm/dp/B000XRQ8UQ/ref=sr_1_1?ie=UTF8&s=sports&qid=1266246724&sr=8-1

Onguard Bulldog (Silver Secure I think) £21.21
http://www.amazon.co.uk/Onguard-Bulldog-Shackle-Including-Cable/dp/B0010VRLGY/ref=cm_cr_pr_product_top


Magnum UL4 Shackle Lock (Silver Secure I think)-£20.40
http://www.amazon.co.uk/Magnum-Shackle-Lock-13mm-120Cm/dp/B00187MCZA/ref=sr_1_2?ie=UTF8&s=sports&qid=1266252560&sr=1-2

Onguard Pitbull Shackle Lock (silver secure I think)- £23.71
http://www.amazon.co.uk/Onguard-Pitbull-Shackle-115mm-Including/dp/B0010VPLPC/ref=sr_1_2?ie=UTF8&s=sports&qid=1266445110&sr=1-2

I first thought that I should go for the Fortum Gold secure one, but then after reading the review on here, it didn't seem such a good choice.
I think the Pitbull is slightly more secure than the Bulldog, is that right?
Or is there another lock I should consider?

Cheers for any advice.