No hard and fast rule once again
Your two options are better rephrased as:
1. 10mbit/s unlimited traffic
2. 1mbit/s unlimited traffic
So... once you look at it from this perspective it's pretty clear since 10mbit/s > 1mbit/s.
To decide on which one, you will have to look at your usage patterns and obviously cost. I would expect option 1 to cost more than option 2
. Burstable is useful if you foresee your peak usage to exceed a certain amount. For example, if you know that you may not use much bandwidth usually, but at your peak times can hit as much as 5-10mb/s, obvioulsy have burstable bandwidth will help towards that cause.
However if you never hit 1mbit/s even at peak usage, then taking the cost factor, you may want to save on cost and take the 1mbit/s.