how to work out what turbo is best?

[SCHWARTZ]

I need a new turbo I have been looking at the gt2860rs but a gt2860r(1) has come up cheap. Here's a comparison of both and a map each.
http://www.turbobygarrett.com/turbobygarrett/turbochargers
This is to be used on my b18ft but how do I work out which one will work better? I know that the rs has a bigger sized inducer and can make more bhp but will that make any difference to me if I most probably won't be able to push the turbo to its limit anyway with the b18ft?

[SCHWARTZ]

Ok well that link dosnt seem to want to work properly but if you tick the box on the gt2860r(1) and the gt2860rs and click compare you can see both maps etc...
Also I don't know how much difference it will make but the gt2860r(1) I'm looking at has a gtx billett comp wheel fired so don't know if that would even the odds?:scratch: