Sigma 105mm f2.8 vs Canon EF 100mm f/2.8L IS

[Ryewolf]

Sigma 105mm f2.8 Macro EX DG OS HSM vs Canon EF 100mm f/2.8L Macro IS USM..

I'm looking to upgrade my current Canon EF 100mm f/2.8 Macro USM to either one of the following... I do have two L Series lens 24-105L f4 and 28-300 f3.5-5.6L so I know the L series are top of the range but is there that much difference other than price between the Sigma (£400) or the Canon L (£900)?

 

[cymruchris]

I've owned both, and have found the Canon to be better at focusing, quieter, and of a much better build quality. You could pick up a used Canon in near mint condition for around £500.