This week's book giveaways are in the Cloud and AI/ML forums. We're giving away four copies each of Cloud Native Patterns and Natural Language Processing and have the authors on-line! See this thread and this one for details.
In terms of usage there is no difference between toString(254, 16) and toHexString(254), just as there is no difference between toString(254, 10) and toString(254), between toString(254, 8) and toOctalString(254) and between toString(254, 2) and toBinaryString(254). There is a difference in implementation which may cause one or the other to be slightly faster, but the difference won't be noticeable unless you call the method millions (billions) of times.