In brief, the 6152e and the GT6152 are the same turbo, if the GT6152 is spec'd with an E compressor cover.
Full Throttle has always called Precision Turbos' turbos GT. In Precision speak, it would be a PT6152E. Both are journal bearing, same thing. In order to get it with a dual ball bearing CHRA, Full Throttle calls it a GT6152BB, Precision calls it a PT6152RE. (E cover, dbb) Both can be upgraded to the TO4S compressor cover or S cover for short. Precision would call it a PT6152S (journal bearing version) and PT6152RS (dual ball bearing version)
It has been a very popular turbo in the Buick community. The dual ball bearing option will help with spool up, typically about 300-400 rpms quicker spool up, journal bearing vs dual ball bearing. But if you're looking for even quicker spool up than just 400 rpms, you're best bet would be too loosen up the stall on your converter. The journal bearing version likes a 3200-3400 stall, where as the dual ball bearing version can get away with a 3000 stall just fine.
Hope this helps.
Patrick