I don't think running a ball bearing turbocharger will start making boost that much quicker versus a journal bearing turbocharger. If you have the time, I found this quite an interesting read.
Better/faster spool with bb over jb is another great misnomer in the turbo community imho and usually a seat of the pants placebo effect. There is also some misconception as to what spool is. The time it takes to start making boost at the manifold, that is really transient response which is generally measured by what rpm you start registering boost at and can be called the boost threshold, then you will have an rpm you achieve desired max boost at, often called full spool. Spool really being time from initial boost to get to desired boost at wot. Most though consider it when boost starts being made, ie my turbo spools up at 3000rpm and full boost 45000rpm.
Many factors to look at but in general no there will be no night and day spool difference especially if the turbo is already spec'd nicely for the engine size. You could expect at most a 100-200 rpm difference tops in boost threshold, ie barely noticeable to no measurable difference going from jb to bb with all other factors equal.
Resistance of the bearings difference is minimal, a couple percent for 360 journal vs angular contact bearings, so all else being the same not much difference in the ability of the mass of the shaft and wheels to accelerate with the same turbine drive pressure.
That said a bb setup is generally mechanically superior to jb in every way. Requires less oil volume and pressure to lube and cool. Less surface area contact so this reduction in friction generates less heat in the bearings which means its more mechanically efficient for optimal acceleration. This also leads to increased stability, as the ball bearings are less likely to deform at higher temps and shaft speeds. A ceramic ball being the best over a steel ball, but steel ball still superior to a 360 journal. To sum it up this leads to bb generally having a longer service life and able to withstand more abuse. It will handle things like surge, stall, shifts, 2-step launches and high pressure ratio/shaft rpm better.
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