Right ... but that still leaves the first question
Oh right ! :o Sorry.
I think both look good, depending on the circumstances.
The fact is that for external shots, full daytime and with such textures, the environment is already quite impressive by itself. In such cases, the bloom really isn't needed.
However, you will not fly in external view all the time right ? And in that case, the effect that you can see in my 737-cockpit shot gives something more. I didn't post any pictures about it yet, but you get also an interesting effect when you fly by night and trigger you cockpit lights. The full cockpit starts glowing, just like if your eyes were used to the darkness, and you feel the need to switch the lights OFF as soon as possible. I suppose this effect (I mean, constraint) exists in real life as well, and this is not something you get with the default FSX bloom or with REX either.
REX will bring you, among many other goodies, very nice clouds. Being often in a plane myself (I do skydive), I can tell that looking at those big white clouds really hurts the eyes, and that's why the pilots wear sunglasses. In FS (9 or X), even with the beautifull clouds provided by REX, you will not get this "glowing" that damage your vision of the external world, and this little mod will bring that quite nicely.