No...as long as its an early case they are interchangable.
Once you get later in the year models things are different but 08 - same.
Yes the 3:1 case IMHO is better in the sand... 4:1 is just too low and you cant get enough runup speed for those big dunes.
No OE setup is perfect, you need to decide on the most common type of off roading you do. If you want to really splash out buy an ATLAS case