It's definitely true that some languages are better than others, because the types of problem and time limitations are the same regardless of the language chosen. Lower level languages tend to be worse because they take longer and there's more ways to trip yourself up.
Personally, I think that C# is the ideal language for interviewing in, as the .NET standard library is very powerful. SortedDictionary alone can easily polish off entire classes of interview questions, and the same can be said for pretty simply LINQ statements. I actually solved one problem so trivially using a combination of the right data structure and LINQ that the interviewer asked me to provide an alternate imperative implementation of the LINQ statement, just so he could see that I actually knew how to implement something like that rather than just use it.
You can approach similar levels of power with use of Java 8's Streams APIs and a good collections library like Guava, but Guava is only likely to be understood by a majority of interviewers at Google, whereas the C# standard library should be understood by a majority of C# interviewers everywhere.
It's absolutely worth spending a few hours brushing up on a "better" interviewing language and then using that rather than using a less optimal language just because it happens to be all you've used recently.