MTRJ interfaces are advantageous because they have a small form-factor.
MTRJ interfaces have gained popularity w/vendors who need high port density relative to the amount of space available for an interfaces' footprint. Chances are, if you look @ any MTRJ module, you’ll find that there simply was not enough real-estate available to build SC-duplex interfaces.
The disadvantage of using this type of interface is that the MTRJ connectors have high insertion loss (when compared to that of SC-duplex). This, however, typically does not logically impact performance when used in conjunction w/ short wave (SX) LASERS. Due to the high insertion-loss, MTRJ interfaces are NOT recommend for use in long wave (LX) LASER applications where greater end-to-end cable distances are often found.
MTRJ is also oddly unique in that most patch cables and/or jumper cables are female/female in gender (this contradicts most patch/jumper cable logic, i.e., RJ45 M/M, SC-duplex M/M). As a general rule, NICs & switch ports w/ MTRJ interfaces are MTRJ M/M so we’d need a MTRJ F/F cable to connect said ports. MTRJ/M cables are reserved for special circumstances (i.e., a fiber trunk).