You can always get an extended battery for the S3, but you can't get a better camera for the HD.
I don't know much about cell service for the VZW S3 but I believe it's at least better than the Gnex. Are you in a weak area, or often travel to one?

 

Personally, I wouldn't trade but that is me. The Razr Maxx HD meets all of my needs and then some.

If you are serious about it, I would make a contract with the person allowing a grace period should you not like the S3. Give you both a few days to try the phone and make sure you don't have signal issues or other issues. Make the $50 be contingent on the expiration of the grace period and should either party wish to return the phone during the grace period, it must be in the same condition as it was received.

I think that is the safest route so both know what they are getting since I believe warranty is only to the original purchaser.

 

It's a bummer about the camera, but if you have to have it, perhaps it's worth the swap. I don't know of any particular threads in the S3 forum, but you can search through to see how folks are with their signal.

 

I might be old school with this though, but to me, a good camera is a nice luxury on a phone not a necessity. The Gnex has a relatively poor camera, but I wouldn't trade mine just to improve the camera. If the maxx serves every purpose you have, and had service problems on your gnex in the past, I would keep it and not go for the S3. If you need a good camera, that's what a standard point-and-shoot digital camera is for and that will always be better better quality than a smartphone.

 

I would not trade in a million years those two phones, but for me the camera is probably the least thing on a smartphone that I use. I'm all about the battery life.

I agree that the S3 is a fine smartphone and since it's been out for quite some time there is a ton of accessories and development for it over the HD. But I also think your statement that the HD camera is 'garbage' is WAY overstated. I've taken a fair amount of photos and video with the HD camera and with the exception of the occasional low-light photo it has performed fine.

 

When I upgraded my family plan, I got the MAXX HD for me, and the RAZR M and S3 for my sisters. I can tell you that the S3 has a very sweet camera. It is much better than the MAXX HD and rivals my 5 year old dedicated Canon point and shoot. I was very surprised. That being said, i am satisfied with the camera on my MAXX HD for what I use it for. I also tested the signal reception on all 3 phones because of the supposed reception issues on the RAZR M. the MAXX brought in the strongest signal, then the GS3, then the RAZR M. In queens, nyc, strong 4G area, same place and time, the S3 had about -5db from the MAXX and the M was about -7db. For comparison, my 2 year old Thunderbolt was a -9db or so. Granted, my average signal on the MAXX HD hovered between -80db to -85db so all phones still had very strong signals. I find 4G gets flaky after around the -110db range.

One thing I have done with my camera is set it on multishot mode. Then i just delete the bad shots. Doesn't work with flash, but i usually get 3-4 good pictures within the 6 or 7 the camera takes.

 

If you get the extended battery from Seido Online, you'll get (almost) equivalent battery life. Not quite as long, but not bad either. Also, if it's Verizon, you don't get GSM unless you root *and* go through gyrations.

 

I have the SGS III (on SPRINT) & it's a great phone.
W/that said, if I everything else is equal & you are satisfied w/the MAXX HD, keep what you have now. $50 over the life of the phone until your next upgrade is a marginal gain @ best.

Besides, if you're interested in a SAMSUNG phone, the S4 is more than likely going to be announced in FEB/MARCH @ probably released mid-late spring. The S3 will seem like an old hat by then.

 

GS3 is a great phone and my wife hasn't had any signal issues, granted we don't live in a weak area.

I think if you want a better camera in your phone then swap if thats what you want. I know some preach use a different camera, but nowadays most use their cell phones, I personally do as well. A lot of folks dont want to carry both, I know I dont.

 

The only two reasons I see to bail would be if you want a better camera and about 17% more viewable display space for apps and web browsing. If those things do not bother you, there is no reason to leave a great device.

Added:

I used to agree about camera phones, but since the JB update, the camera on the GS3 is as good and fast as our stand alone cameras. No optical zoom on the GS3, but the only phone that did have that was the N900 and it SUCKED as a smart phone and phone in general.

 

Have you considered that maybe your wife is just a better photographer than you? Just kidding!

I have not experimented a lot with my camera on the HD. I've taken a lot of photos but they have all been sitting perfectly still and usually well-lit. Since my kids are college age they never move fast but rather seem to move about as fast as a three-toed tree sloth!

My previous phone was an iPhone 4 which took excellent photos and video. We went to an Aerosmith concert and had front row seats and the photos and video clips I got from that were incredible. Sure there was a lot of crappy ones but the iPhone definitely is one of the better camera's out there in phone land.

So I guess it comes down to just how important the camera is to you. Obviously if you have little kids you will need to be able to get those quick shots. Since your wife has the iPhone 5 she will be able to get them. It would seem a pretty easy choice for you - just weigh out your differences of importance and go from there.

 

For what it's worth, the cell reception on my SG3 has improved since the JB update. I can talk on the phone in my office now, whereas I had to step outside before. The camera in the SG3 is much better than the RMHD. I have both phones, and while I love the sturdy build of the RMHD, I generally prefer the SG3 for everything else.

I had a problem with MediaServerService burning up my battery, but I formatted my SD card, and used and app called SGS Toolbox to scan for corrupt thumbnails, and it seems fine now. Battery life is back to excellent.