Complex Samples (IQ) - Baseband Filtering

A real signal is complex conjugate symmetric, so any filter over $-fs/2$ to $+fs/2$ is really only unique over the range from $0$ to $fs/2$. This would be a primary motivation for working with a fully complex signal as the unique range is then truly extended over the full $-fs/2$ to $+fs/2$ range.

Another more dominant reason to implement a complex filter besides the bandwidth requirement outlined above (where the choice is really sample twice as much or carry two datapaths; similar complexity and certainly you could map either to be similar if that was the only goal) is when the passband itself is not symmetric: specifically as a bandpass filter when the positive frequency passband is not equal and magnitude and conjugate in phase to the negative frequency, or as a baseband filter- the passband shape itself is asymmetric or perhaps completely one sided. Another dominant reason is when real signal conditions would create images very close to the signal where further filtering would be difficult, such as if conditions require operating very close to the Nyquist boundary. If the OP doesn't have these conditions, I don't see a strong motivation for complex filtering, which requires 4 real multipliers for every complex multiplication operation (assuming complex inputs and outputs).

Channel equalization is another example where a full complex filter is often necessary (as an implementation on a baseband signal) but not needed for a passband signal.