Hi: I think it really depends upon many things. If it is narrow bandwidth, you may be able to achieve very good ground at a particular frequency usng 1/4 lambda. However, the 1/4 lambda stub will not work for wide bandwidth. Grounding via should give reasonable good ground over relatively wide frequency range from 0 to some high frequncy. However, it will have some inductance there and this inductance will become more and more important at high frequency. Regards.