Yes, the EZV has RTS, but it's flaky at best. RTS isn't really any better on my SCDS2, though, so if that's the most important feature to you I wouldn't look there either. I don't have any idea how it is on any of the other carts that offer it.
Since the EZ Flash team makes both the EZV and the 3-in-1, the EZV's support for the 3-in-1 is pretty obviously top notch.
I don't know why people seem to think the EZV has low compatibility, that's just not true. I'm not saying there aren't some problem games, because there are, but I can only think of one broken game on the 3.X kernels that I give a crap about (Puzzle Quest 2) and it works on the 2.X kernels.
Out of the SCDS2 and the EZV, the EZV is my preferred cart to use. Mostly I only use my SCDS2 for the things that take advantage of it's CPU. Beyond the cheat maker (which I rarely use) on the SCDS2 there really isn't any other reason for me to use it over the EZV... And I dislike the SCDS2 interface, and while BAG Plug and iMenu are great, they still don't fix the things that keep me using my EZV.