而 vs 二， are they same in pronuciation except the tone?

[Mugi]

Am I the only one that finds it practically worthless for non-native Mandarin speakers to compare how they pronounce ér, ěr and èr and determine if there is a difference or not? Commenting on whether a native Mandarin speaker pronounces them differently is somewhat more meaningful, but unless the pronunciation is tested in a scientific manner, it's still very much subjective.