Tim,
You would be more than happy with either the Omni 4000 or the Iwata Eclipse CS if you want to spend an extra $20 more.
They both hold 1/3 oz. of paint which should be enough for most paint jobs unless you plan on painting a 1/48 scale AC-130 Spectre, in which case you might as well buy a Sata spray gun.
I like the Omni 4000 and just received one from Dixie Art a few days ago and am anxious to give it a try. The Iwata's are a little smoother and a little more precise in the hands of a skilled airbrush user, but I would say they are not a necessity for a beginning airbrush user, or even an advanced one for that matter. The parts are more expensive in the Iwata's and their customer service isn't even close to what Badger's is, who now make the Omni as you probably know.
So choose which one you like, buy it, and you will be happy.
Actually, I would buy the Omni 4000 and if after using it you think the Iwata would be better, then you could sell the Omni no problem.
Mike
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon