In Junit 4, do you see any drawback to throw a ComparisonFailure instead of an AssertionError when assertEquals(Object, Object) fails ?

assertEquals(Object, Object) throws

• a ComparisonFailure if both expected and actual are String
• an AssertionError if either is not a String

@Test(expected=ComparisonFailure.class )
public void twoString() {
    assertEquals("a String", "another String");
}

@Test(expected=AssertionError.class )
public void oneString() {
    assertEquals("a String", new Object());
}

The two reasons why I ask the question:

• ComparisonFailure provide far more readable way to spot the differences in dialog box of eclipse or Intellij IDEA (FEST-Assert throws this exception)
• Junit 4 already use String.valueOf(Object) to build message "expected ... but was ..." (format method invoqued by Assert.assertEquals(message, Object, Object) in junit-4.8.2):

static String format(String message, Object expected, Object actual) {
    ...
    String expectedString= String.valueOf(expected);
    String actualString= String.valueOf(actual);
    if (expectedString.equals(actualString))
        return formatted + "expected: "
            + formatClassAndValue(expected, expectedString) +" but was: " 
            + formatClassAndValue(actual,   actualString);
    else
        return formatted +"expected:<"+ expectedString +"> but was:<"+ actualString +">";

Isn't it possible in assertEquals(message, Object, Object) to replace

fail(format(message, expected, actual));

by

throw new ComparisonFailure(message,
    formatClassAndValue(expectedObject, expectedString), 
    formatClassAndValue(actualObject,   actualString));

Do you see any compatibility issue with other tool, any algorithmic problem with that... ?