It depends.
There is no doubt that out of the three objects we have introduced so far (ts, zoo, and xts), the xts class is the most advanced and friendly to use. Moreover, since the xts class is also a zoo class with additional functionalities and improvements, the question actually should be xts or ts—which one to use? This mainly depends on the type of packages and applications you are using for time series analysis. However, in my mind, working with xts objects has more benefits compared to ts objects, since most of the forecasting models in R support only ts objects.
On the other hand, if you're not bound by requirements or if you just want to slice and dice a time series object, it is highly recommended that you use the xts (or zoo) object. The good news here, as we saw in some instances, is that both the xts and zoo...