4:11 would be a higher ratio.
3:55 would be a higher speed.
you will go faster per a given rpm with the 3:55 rearend.
top speed would be dependent on the abilities of the engine.
There are gear calculators on alot of websites that will allow you to plug in different combinations to see what rpms you would be turning. Randy's ring and pinion is one that comes to mind.
How about some background info. What exactly is it that you are trying to accomplish?
