Efficiency: list or tuple?

[Spencer Ernest Doidge]

I'm interested in putting pairs of integers and floats into a sequence 
of indeterminate length.
I'm collecting this data in real time, and I want to use the most efficient
available method so as to be able to gather data as fast as possible and
append it to the sequence as I go. 
As far as I can tell, I have lists and tuples to choose from. 
Does either of these structures work better in this situation, or is
there some other way I don't know about?

-- 
Spencer Doidge