Compressor housing a/r has a much less significant impact on performance than the exhaust side. There shouldn't be any difference in cost tho, so you might as well get the .60. Just make sure whatever you get is appropriately machined for the wheel you are using. The .73 HKS exhaust housing (t2 footprint) is only like $160, which is cheap in my opinion. Do you need the t3 flange for some reason?
andris
andris