They are the same toner however the option ending in X is the high yield toner with up to 12500 pages.
HP 952XL has a shelf like of 36 months, and a yield of 1,600 pages.
The HP CE278D Toner is a 2 pack of the HP 78 A Black Original LaserJet Toner Cartridges and contains two (2) of the HP 78 A Toner Cartridges. HP CE278A contains a single (1) Toner Cartridge.
This machine takes an individual toner for each color along with a waste toner bottle and photoconductor unit. The item you are inquiring about is the photoconductor unit. The toners needed are LEXX950X2YG, LEXX950X2MG, LEXX950X2KG, LEXX950X2CG and the wate toner bottle is item LEXC950X76G.
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