Hi,
Did you read the datasheet?
It says 1V VCE with 2A ... but this is with 0.2A of base current, which I assume you dont have.
Less base current, higher dropout voltage.
For less dropout voltage you should consider to use a MOSFET.
choose one with
* Low V_GS_Th, much less than 3.3V, they are often called "logic level" Mosfet
* low R_DS_ON. It should be less than expected_dropout_voltage / expected current.
Almost any MOSFET manufacturer and any distributor provides interactive selection guides for choosing a suitable MOSFET.
Klaus