def get_best_capabilities(capabilities):
    """
    Returns the best capabilities based on performance and stability.

    Args:
        capabilities (list): List of tuples containing capability name, score, 
                             iterations, and time taken.

    Returns:
        tuple: The best capability with its corresponding values.
    """
    return max(capabilities, key=lambda x: (x[1] + x[3]) / x[2])

# Example usage
capabilities = [('evolved_verified_generate_test_1768680667', 4235.89001196408, 51, 8305.7),
                ('verified_default', 4235.0, 51, 8303.9),
                ('evolved_verified_fib_fast_1769055768', 4235.0, 51, 8303.9)]

best_capability = get_best_capabilities(capabilities)
print(best_capability)