Ah, well, best depends on what you plan to do with the phone. Moreover, it's important to note that one (the Omnia) is a smartphone while the other two (LGs) are just feature rich. You also are required to get the data plan ($30) with the Omnia; all smartphones require it. You are not required to get a data plan with the LG devices, unless, of course, you want to use data; if so, you can get the $15 VCast package or get a premium or select plan. Still, if cost isn't a factor, just remember that the Omnia is a Windows Mobile phone and while it can arguably do more than the LG devices it does come with all the virtues and vice of Windows Mobile. (I'll let someone else speak to the virtues and vices of Windows Mobile.)
As to the Versa and the Dare, they are essentially the same devices. About the only real different is that the Versa comes with a detachable physical keyboard. Otherwise, all the phones are touch screen based. Software wise, though, the Dare are the Versa are similar; it's just that one (the Dare) has a more customizable UI, but the "nuts and bolts" aren't that different. Also, the Dare has a slightly better camera.