Multi-Stage digital FIR filter vs Single stage FIR filter. Which is better?
First, two cascaded 24th-order (25-tap) filter will yield a 48th-order filter which is not identical to a 49th-order (50 tap). However, as I assume that this isn't really the answer you are looking for, but rather the difference between multi-stage and single stage.

Assuming infinite precision arithmetic they are the same. In practice, multi-stage filters have lower coefficient sensitivity, so using two (or more) filters would (statistically) allow shorter coefficients word lengths. However, multi-stage filters also require intermediate quantization, so for a complete comparison one should also consider that. And, as obvious from the first paragraph, multi-stage require more multiplications for a given filter order. I would say that unless you run into problems with coefficient quantization you should go with a single stage.

Another use case where multi-stage is relevant is when implementing interpolation and decimation. By using more than one stage some of the filtering can be performed at a lower sample rate and the total arithmetic complexity is reduced.