MNS vs SYR

Hi guys
if anyone would be willing to lend a hand and give me a bit of inside knowledge on the differences between the two???
MNS has an npv of $1.69 bill and an IRR of 98% vs
npv $1.125 bill and IRR of 70%

i think its the product basket price that makes the difference $2350 vs $1000 for SYR.
Capex is $289 mill vs $144 for SYR
SYR has a 40 yr mine life and MNS 15-18 years.

any thoughts and comments would be appreciated

cheers