Well, I have the FSA ACR headset so I can't say if that's what comes with the A9. If the A9 set-up is not the same, the genuine FSA ACR headset is a worthwhile $50 investment. The FSA compression plug doesn't slip and is definitely longer than the TanTan plug, which is most likely the same as the Velobuild set-up. The FSA plug supports the stem better than the stock plug. I feel like all the FSA materials are just higher quality than the stock TanTan components for sure.
Way more important than the individual components, though, is the way the FSA headset/Metron handlebar system works together. Instead of trying to cram all the the tubing and cable housing through one narrow choke point through the compression ring, the ACR system routes the front hydraulic brake tubing through the top of the stem, over the top of the steerer tube, through the compression plug, then down through the tube/fork. I have to believe the FSA/Metron system is easier to work with and won't cause the same problems with tubing/cable routing.
I'm just not willing, at this point, to fork over $400-$500 dollar's for a set of Metron handlebars to fit on my $550 frame and budgetish build. Along those same budget lines, I suppose if you're gonna go with electronic shifting, it won't matter as much as far as I'm concerned.