It's good enough.
These days, either engine type can be made to be as smooth and/or powerful as it needs to be. Lighter internals go a long way toward mitigating vibration. I guess if you're really trying to push the limits of smoothness, you'd still prefer an inline-6, but I have a hard time imagining an application like that. It's more common to see applications where all you care about are power and compactness, and in those cases a V6 is a great call (e.g. Nissan GT-R, Ford GT, Acura NSX).
AFAIK, the main reasons to recommend one configuration over the other are packaging and development cost. Mercedes-Benz recently said they'll be phasing inline-6s back in, partly because they're producing a ton of inline-4s and it's super easy for them to derive an inline-6 by just tacking on 2 more cylinders. BMW has been all about inline-6s for a long time and has basically zero invested in V6s, so it makes sense for them to stick with inlines. On the other hand, if you're Hyundai, Nissan, or Honda, you're already make a ton of V6s to fit into FWD economy cars, so you probably won't be tempted to make an inline-6 even if you design a car that could be made to accommodate it (e.g. Genesis, GT-R). Audi is in a similar boat because it draws so heavily from the VW parts bin