Is there a perceptible difference between using
I'd suggest that it is better practice to use
String.format(). The main reason is that
String.format() can be more easily localised with text loaded from resource files whereas concatenation can't be localised without producing a new executable with different code for each language.
If you plan on your app being localisable you should also get into the habit of specifying argument positions for your format tokens as well:
"Hello %1$s the time is %2$t"
This can then be localised and have the name and time tokens swapped without requiring a recompile of the executable to account for the different ordering. With argument positions you can also re-use the same argument without passing it into the function twice:
String.format("Hello %1$s, your name is %1$s and the time is %2$t", name, time)