Well, wx-2.5.4 looks better if you use gtk2, but it uses more memory than with gtk1. The future (very near future, indeed) is wx-2.5.4, because soon wx-2.6 will be out, and then we will no longer support wx-2.4. But in terms of functionality, it is the same.
Well, there is one difference if you want UNICODE. Then you will have to use gtk2 compiled for unicode. AMule has support for it and runs fine.