The period of a 50 Hz sine is 20 msec. Is an entire cycle needed before a frequency detection can be realized or will a partial cycle provide enough information for detection of the frequency? My feeling is that an analog filter will provide some output before one cycle completes but a digital filter needs at least one cycle to provide enough information to identify the frequency.
Digital does require less hardware and is changeable on the fly (you can vary which bins you look at).
I'd read that IIR has a faster response than FIR and its computations are simpler, but IIR can't use integer math like FIR so how is it faster and simpler?
Any filter can use interger maths in the form of fixed point arithmetic.
I've seen numerous references to well known numerical overflow issues with biquad direct form 2 when implemented using fixed point.