Some great info and links in the Posts above. Here is my 2 cents.
The advantage of using 4 ball bearing races instead of just bushings+shaft is simple.
The bushing+grease system is designed with clearance between the mating parts .There must be a little free-play for the mechanism to move.Hopefully that clearance is parallel/centered and aligned ! Over time, any metal-to-metal contact between the bushing and shaft will increase the freeplay. Some shifters use Aluminum bushings and a steel shaft ,so the wear will be quicker.
By contrast, Ben's bearings are an interference fit in the bushings and on the shafts. The bearings are sealed and pre-lubed. There is no free play, none. The advantage seems small but is multiplied by the length of the shifter. Ben's shifter is adjustable for height - just like the OEM part. You can adjust it almost as high as stock if you wish. At that height, the advantage of the bearings is more apparent.
I hope this helps.But Ben is not making his shifter anymore so the point is moot.He is working on a 4.0L Boxster project !
For more, see Post # 480 & 476 here:
Ball bearing short shifter !
There are cheapo generic 997 shifters on EBay for less than $50 if that is the objective. You will notice they are very similar to the name-brand ones offered at x4 the price.And none have bearings -just bushings !