MCU 3.3v to 5v Relay Driver, MOSFET or BJT
The BSS138 is not characterized for Rds(on) with 3.3V drive, and the MMBT3904 is not characterized for Vce(sat) at 75mA so neither one is great. 

There are plenty of better parts such as MMBT4401 or AO3414 that are properly specified to work reliably. Either one will work fine, with the proper choice of base resistor etc.