[AndreyAkinshin]

Removing redundant comparison with "null" ((!(obj is Vector)) is superset condition for (obj == null))

[mellinoe]

Looks reasonable to me.

[mikaeldui]

Isn't "obj == null" a lot less expensive than "is"?

[AndreyAkinshin]

@mikaeldui, yes, but in the case of a non-null obj with wrong type, the whole condition will more expensive.
I think, we should remove the redundant check.

[joshfree]

👍 LGTM

[stephentoub]

I ran some microbenchmarks, which were either inconclusive or slightly favored the change. Given that, and that this change makes the code cleaner, LGTM2.

[robinwassen]

Feels like quite a minor improvement - but Andreys solution is more favorable than the existing since it does not try to outsmart the compiler.

There is also a third style that could be used that looks like the following:

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public override bool Equals(object obj)
    {
        Vector2 v = obj as Vector2;

        if (!v)
            return false;

        return Equals(v);
    }

Hard to tell which one is nicest, but guess it does not matter that much since this issue probably won't have any real impact on the readability or performance.