Hello Anthony,
I have a couple of the old style lithium batteries and quite a few of the ni-cad ones.
The lithium are better and a lot lighter, also they discharge giving full power coming to an abrupt stop, there is also a charge state led indicator on the battery.
The lithium batteries don't mind the cold so much.
I can't remember the price difference but if you are replacing a failed ni-cad it may be worth a punt and try one, But just check your charger is the red one because the black ones cannot charge lithium batteries.

HTH,
Ian