I have the Evo 3D with Sprint right now, and here's what I think of it after a month of usage:
Battery life isn't as good as my Atrix, and the voice quality isn't as clear. I have heard there's fix available, but you must acquire the MSL from Sprint. I haven't tried it but apparently it made things much better for everyone that tried on Androidforums.
The size is certainly bigger than the iPhone or the Atrix, but it wasn't as big of a deal as I thought it was going to be. The extra screen space is nice, and the screen is very pleasing to the eye. I cannot stand going back to a 3.5" screen any more, but I don't know how big the new iPhone's screen will be, I hear 3.7" but that's still a lot smaller than 4.3". Anyways, the screen on the Evo 3D is brilliant. I read some reviews that said it wasn't nice, and I think those reviewers are either biased, blind, don't know what they're talking about, or a combination of the above.
One thing I wish HTC optimized better is the auto brightness settings. It never goes below 25% from what I can tell, even when I'm in a dark room w/ the lights off. You can always adjust it manually, but I expected more from HTC.
I don't know what the iPhone 5 will be like, but from the rumors I've heard it'll have a dual core processor like the one in the iPad 2, maybe more RAM (maybe not), a better camera (8mp), larger screen (3.7"), and a different form factor (tapered back). I've also heard they're having issues w/ heat and battery life w/ the dual core processor, so I don't know if it'll have those issues. But in general, you can expect the hardware to be pretty on par w/ the Evo 3D. Although I would expect the camera to be much better on the iPhone.
Camera wise, the one on the Evo 3D is pretty disappointing compared to the one on the Atrix. It's okay in daylight or brightly lit environments, but low light performance is pretty bad. Mine shows a green tint most of the time, and the lag to take a picture is pretty long. Friends' iPhone 4 definitely has a better camera. I really think HTC could've improved here, but they didn't
The biggest difference I think you should focus on is the software and the environment. If you use iTunes a lot, and generally don't like to tinker, iPhone is the better choice for you. Lots of improvements are coming in iOS 5, and generally things are more stable in the iOS environment (no runaway apps, etc).
If you like to tinker, Android is the way to go. HTC unlocking tool is coming and the Evo 3D will be unlocked come September. I like Sense 3.0 so far, but it's very memory intensive, so I can't wait to see what CM7 is like on the Evo 3D. But once you get it rooted, you'll get a lot of options on your phone that you cannot do on even a jailbroken iPhone.
When are you upgrading? If you can wait until November ish, I'd take a long look at the Nexus Prime. It's supposed to be a beast w/ the TI 4460 CPU and a 1280x720 display. Oh, and Ice Cream Sandwich ofc