When to use

Definitely use

• If you have many samples (>100) but the more, the better.
• If you have mostly Integer values in your Genotype fields (e.g. AD, DP, PL).
• If .bcf already provides an advantage over .vcf.gz for your files.

Maybe use

• If you have at least some Integer values, but also float/char/string values.
• Check whether the options for compressing float/char/string reduce file-size or not.

Don't use

• If you have no sample data or only a single-sample [it shouldn't increase filesize, but there is also no benefit].
• If you have only float and/or string data fields, and they are not compressible with the optional encoders (try this first!).