how to select filter prototype?base on what?

base on below
1.lower order
2.maximum capacitor to minimum capacitor ratio,lower
Anyone can give further information

Although the filters may have the same basic topologies the value of filter elements determine filter properties. These are flatness, passband ripple, steepness, stopband attenuation, group delay characteristic etc. Each filter type has it's own transfer function usually named by inventors name. These are Gaussian, Bessel, Butterworth, Legendre, Chebyshev, Hourglass, Eliptic etc.