As far as a method with single parameter is concerned not much difference is involved. However few good points can be consider in case of ELLIPSIS(...)
1) There can be ONLY ONE ellipsis parameter in the method and which MUST be the last parameter. There in no such restriction for String version
2) It can be analysed using int printf(String,...) method of C Programming in which it can accept variable number of arguments. like printf("%d",1);printf("%d%f",1,1.0);
3) Elipsis provide a way to define single method defination for variable argument calls with ZERO TO 'N' number of arguments of same or type that can be IMPLICITLY CASTED to that parameter.
4) Ellipsis version comes with 5.0 version.
5) Ellipsis provides more freedom as compare to array version.
No hard rules which to use when.