If you had a choice to acquire one of these balls, which ball would you choose?

Nothing wrong with Cell Pearl, but Gravity Shift was better for me, especially on flatter patterns inside. 

I think this is a style issue. Which ball fits your style? For me it is the Cell Pearl. I'd be able to use that ball in a wide range of situations.

However, avabob is correct, since that Gravity Shift was a serious skid/snap ball to me, and very useful on flat conditions.

I liked the gravity shift and virtual gravity.  Really didn't care much for the strong asymmetric pearls that Storm followed up with for awhile until Lucid came along.  Again, I am talking about controllability and power on flatter tournament patterns, not house shots. 

Yes on longer flatter patterns, not on shorter patterns.  G Shift and VG were good because they could be rolly even with a strong change of direction at the breakpoint.  Most longer patterns force you inside sooner or later, and that is where those balls stood out for me.