mtn or cell data

Hi guys,
I use mtn at the moment for my Internet, I use it with either a mtn dongle or in my tablet, tablet is samsung 10.1 lte,

I am on a pay as you go, I buy mtn for 1 gig at R150, connection is excellent in my opinion,

I got a call today from fnb offering 5 gigs a month at R119 per month with a dongle for cell c,

Should I change, I use about a gig a month, but will get really irritated if diwnloads take long,
I stay in lenasia south connection seems good for the area, but cant pinpoint my street,

Your advice