hi zulkarnain…
Butterworth filters are used in applications where maximum pass band flatness is required
on the other hand Bessel filter is a linear form of filter that provides a maximally flat group delay or propagation delay
across the frequency spectrum, but offers a slower transition from pass-band to stop-band than for other forms of filter of the
same order.
Bessel filter is not used as widely as the Butterworth of Chebyshev filters for RF applications, although the fact that it has a maximally flat group delay means that Bessel filters are often used in audio applications such as audio cross-over networks.
with regards