Most engineers default to LIR2032 because it's the obvious CR2032 replacement. That's usually correct — but for an industrial PCB that has to be reflow-mounted or run hot, ML is the only sensible choice. Here is how we steer customers.
Voltage and the regulator question
LIR (Li-ion) sits at 3.6-4.2 V, ML (Li-MnO2) at 2.8-3.0 V. If your circuit was designed for a CR2032 (3.0 V) and you can't add a regulator, ML drops in. LIR needs an LDO or boost depending on the load.
Reflow compatibility
Only ML survives standard lead-free reflow profiles (260 °C peak). LIR cells must be hand-soldered or socket-mounted.
Cycle count
ML offers 1,000+ cycles vs. LIR's 500+. For a daily-charge wearable that's 1.4 vs. 2.7 years of design life — usually a deciding factor for product warranty.