Ah... something I can answer with confidence... a solicitor-advocate is precisely what it says! About 6 or 7 years ago certain solicitors who took a special course in, wait for it - advocacy - were allowed rights of audience in court but only up to... errr... here's where my confidence evaporates - I forget which levle of court, but essentially they get to do what a barrister does in terms of rights of audience in court.
And I'd be inclined to go for the BVC - there's nothing worse than setting your sights lower than you ought to do. If you think you've got the ability the dedication, the confidence and self-assuredness, go for it.