BB front squats challenge shoulder and wrist mobility.
KB front squats challenge shoulder and wrist stability.
Both are useful things to have.
KB can be difficult to progress on, since after 16kg they are usually only available in 4kg jumps, so your doubles will be 8kg's difference. Imagine having to progress BB front squats in lots of 8kg only. However if you are working out for general health, some everyday strength and joint mobility, that won't matter, you'll be happy at some particular weight.