Why pick ONE at all? You seem to be presenting a false dichotomy - or trichotomy, if you will - that there are people who are 'armchair activists' who write to newspapers and their MPs, people who are community advocates as you describe above, and people who go on demonstrations. I don't think you can these activities as disparate and divorced from each other - they feed into and complement each other, and very often it's the same people doing all three things! I'm a charity worker, I lobby my MP on issues that matter to me, and I go on marches and demos when I can. I very much doubt I'm alone in this - or in thinking that all these things are worthwhile, and within my rights.