Which iphone 5s deal should I go with?

So I'm gona buy an iphone and there are 2 companies providing this, the first company offers a contract of 50$ Per month (175 dirhums) for 32gb with 1gb data and 24 months contract - 2 years

While the other company offers a contract of 70$ Per month (250 dirhums) for 16gb with 2gb data and an 18 months contract - 1 year and half

Which one would you go for
Currently I'm using the sim of the second company so if I decide to switch to the first company I would have to change my number

And please don't suggest me another phone
I'm satisfied with Apple only

Get the nexus 5