Excellent info and got me thinking on the choices! So if I were to go TRX-4 as many have mentioned here, do I go Sport kit or the higher end kit? I do realize that the TRX-4 has a TON of aftermarket support and any LHS (whatever is left of them) will carry parts.
I'm going to go and take a look at the SSD videos...
As for SSD yes look at videos and research it. I have not had the chance yet to try this rig but from the consensus on this forum it is a great build, very scale, non portal, rig.
As for TRX-4 Sport vs the other variants with 2 speed / unlocking diffs, it would come down to the following differences:
Sport:
Lighter body with minimal scale accessories for better pure crawling experience. No unlocking diffs, it will trail fine but for trailing the unlocking diffs are nice. They are not needed just a nice feature.
Some want a pure crawler and go for the sport because it does not have all the extra bells and whistles they don't need and it is lighter for better side hilling and climbing steep inclines etc... This does not mean it cannot trail great, most people make this choice when they want more of a crawler or sometimes due to budget and they can add the other options later on if they want to.
Bronco / Defender / Blazer etc:
These rigs are more scale obviously. They have larger bodies with more scale accessories that will challenge the rig when pure rock crawling. They still rock crawl great but the large heavy body can get hung up on rocks more easily and it will be more tippy on side hilling and steep inclines etc...
This setup comes with the 2 speed which is nice for when trailing as well as the unlocking diffs. This gives a more scale experience and makes the rig handle higher speed turns with unlocked diffs. You cannot go full speed and cut the wheel but it will handle a higher speed turn better thus better at trailing.
Now either of these rigs can be modified easily to suite your desired driving style and terrain. If you feel the 2 speed with unlockable diffs is not something you are interested in go with the sport or SSD trail king. If you like the 2 speed with unlocking diffs go with the bronco blazer etc.....
You can always make changes to either model to dial it in to your preference. If you go sport route and want the unlocking diffs you can purchase and add after albeit at a bit higher cost than getting it from the start. And if you go with the Bronco you can always remove the unlockable diffs as some have done this to lighten up the rig when they feel it would provide a better crawler experience.
Bottom line you cannot go wrong with any of the choices. They are all great platforms. I think you need to decide what rig fits your driving style best.
I mean honestly between your OG SCX10 and the SSD Trail King / TRX-4 there is not a huge difference in driving experience. All of those are scale with narrow axles and 1.9 wheels. The portals will make the other rigs handle larger obstacles better and the new rigs are built with better quality plastics / parts etc.
The Capra will be more of a different experience driving. It has portals with 2.2 wheels and wider axles. This rig will handle pure rock crawling better out of the box effortlessy. Since you say "light crawling" I am thinking you may get bored with the Capra as it will just roll over that stuff like it was on pavement.
**EDIT**
Oh BTW I was in the same position as you are now. I have the 2012 Rubicon OG SCX 10 too. I also have an OG 2.2 Wraith. I ran with these since 2014 as nothing came out that really made me feel it was worth spending the money over what I already had.
Back in Dec I was bored and wanted to try out the TRX-4 due to unlocking diffs and 2 speed. When I got it my OG SCX did not sit on the shelf. I still loved my OG and drove both. The most noticable difference with the TRX-4 bronco was that it could clear larger obstacles due to the portals but my OG SCX10 was more planted with a droop suspension setup. It would belly drag over obstacles the TRX would not but it could side hill much better and was more planted on more difficult terrain. The Driving experience with the Bronco was more fun trailing due to 2nd speed and the unlocked diffs. Additionally it was just fun to play with those options.
When the SCX10 III came out I had to get one as it was the first Axial rig released that had enough changes in design for me to warrent the price. I love the SCX10 III mostly due to two factors for me: A. It has dig which I love when crawling and B. it has the lower ratio transmission gears. I am able to gear it down to almost 100:1 and then put in a large motor. Currently setup with Caslte Slate 3800Kv and get 6MPH in first and just under 9MPH in second. I do wish as others that there was more of a speed difference between first and second however. Due to minimal speed difference and no unlocking diffs I think you would be happier with the TRX-4 with your stated purpose for the rig. The Fiance will enjoy it more IMO for trailing and you will enjoy it more for crawling as it does both GREAT! Had you said you wanted more of a dedicated crawler I would have suggest the SCX10 III only because I find the dig function more useful than unlocking diffs when pure crawling and especially technical crawling.
If I am on my rock course I take the SCX10 III more often than the TRX-4. If I am trailing the TRX-4 gets the nod. Both trail and crawl great and I use both for those purposes. I just trail more with the TRX and crawl more with the SCX purely due to enjoying dig more when crawling and unlocked diffs when trailing. If I had to give one of the two up it would be a difficult choice as I love both. I say this to enforce my statement that you cannot go wrong with any of these choices. They really are great rigs. Make a decision and down the road you may buy another just to have something slightly different that you enjoy. A second also is great for times when one breaks down and you are waiting on parts!