[myTouch 4G Q&A, Help & Troubleshooting] c_licious:
Was sitting in the same boat. Got the G2 first (coming from a Nexus) and decided to give the MT4G a try when it came out.

Looks and size:

At first I found the G2 a lot more aesthetically appealing although I immediately noticed how much thinner and lighter the MT4G felt. Coming from the N1 it took a bit of adjustment to get used to the size and weight of the G2 and the physical keys on the MT4G. Having said that I really like how the G2 lays in your hand when you're web browsing with the keyboard open.

Look wise the MT4G is definitely not a Nexus 2. In my opinion the aluminum rim looks a little out of place and I don't like how the battery cover doesn't match with the colors on the red and plum model. On the black model the aluminum does not stand out as much because it blends in nicely with the black. Since it's more subtle it actually ends up looking quite good. I definitely could have gone with soft buttons instead of the physical ones but that's my personal preference.

Keyboard:

Whether you want a keyboard or not definitely comes down to personal preference. It's nice to have one but you pay for it in additional size and weight. The keyboard got great reviews so I assume a lot of people like it. I personally wasn't a big fan. Typing seemed slower and more strenuous than on my G1 because of the large keys and lack of dedicated number keys. I would have liked it better with 4 rows instead of 3 (bringing back the numbers) and smaller keys to start with. I also never quite got used to the special function keys HTC decided to add. Due to their prominent positioning one is quite prone to accidentally hitting them.

One major flaw of the keyboard is that you have no control over the keyboard backlighting. Until some custom rom fixes the issue, the light will come on and off and on and off etc when you're inside because the light sensor can't make up its mind. I found myself more than once covering the light sensor with my finger to force the backlight to come on because I had problems seeing the keys in the light condition I was in and had no way of forcing it to stay on.

Build quality:

When you put the phones next to each other you'll notice that most of the materials are the same. Both have metal battery covers and use hard rubber for the rest. Even the screens are identical (despite some rumors going around). The main difference is the front of the G2 with the soft keys vs plastic physical keys on the MT4G. G2 wins hands down in that area but I don't think this difference is nearly as significant as the controversial hinge when talking about quality and durability. I guess only time will tell how that'll play out. Considering how many people have sent their G2 back because of the hinge you should be prepared that it MIGHT be a problem in the long run.

Operating system/interface:

Since we have root there's really no point in comparing sense (+ genius button) to stock since you'll eventually be able to run either one on either device. It might be more important to consider dev support. So far the G2 seems to have more support but you also have to keep in mind that the MT4G has barely been out for a week. That considered it still got root the same day the G2 did and ClockworkMod recovery was ported to the MT4G 8 hours after the G2 got it. I even already saw pictures of a MT4G running an experimental version of CyanogenMod 6. Since the devices are so similar you can expect that most stuff for the G2 will be ported to the MT4G rather quickly and vice versa. One other thing to consider is that video chat will probably be an integral part of gingerbread. Makes me wonder how the G2 will hold up in the android 3.0 era (although I'm sure custom roms will work around it).

Unique features:

G2: keyboard, click mechanism for battery cover

MT4G: front facing camera (FFC), 256MB additional RAM, 100 mAh better battery, hot swappable micro sd card

Verdict:

Both are great phones. I ended up picking the MT4G (black) because size mattered more to me than the keyboard and I liked the additional ram. I also liked having the FFC. Those are things no custom rom can add and ended up mattering more to me than aesthetics. I also noticed my hinge getting slightly looser during the 3 weeks I had the G2 which worried me a little. If you want a keyboard however, or really dig that clean cut business look, the G2 is your phone. Good luck deciding.