Is there any advantage on using a low span value in a RRC filter? I know that in a RRC filter a high value of the span gives a better response, in the sense that the RRC filter response is more near to the ideal RRC filter response. However, would there be any advantage on using a small span?

Lets say, for example, that I am sending 100 BPSK symbols, a value of span = 10, would be better, in terms of the BER, than a span = 2. 

Q: But would there be any advantage with span=2?
The advantage of a RRC filter with a smaller span is that it has fewer taps, so the filter requires fewer multiplies and additions per sample.  Longer filters approximate the ideal RRC response more closely but require more computation.  Shorter filters do not approximate the ideal RRC as well but require less computation.  Typically, one will choose a filter length that strikes a balance between computational demands and performance.