So, I got new tires. This provided an opportunity to test both kits. On the old tires, I decided to drill some holes and plug them. After using both the Extreme Outback and Safety Seal kits, I'm not sure I can claim a winner based on the actual plugs. Both seem to plug the hole and would never come out on their own. As for the tools handles, reamers, and insertion tools, I'm going to lean towards Safety Seal. Although the EO handles are solid metal, the SS handles feel better in my hand. The SS Reamer is more substantial, but at the same time is much bigger. Having both is nice. The real difference is in the insertion needle. The SS is thinner, plus there is a retention T on the insertion needle that is a nice feature. It may not be needed, but it is nice to use the retention T for peace of mind knowing the plug will not be pulled back through. Both plugs, work with both needles and all the EO tools fit in the SS handles.
So which is better, I feel it will be personal preference. Neither is lacking in quality.
If you want the most complete kit, EO wins hands down. The addition of all valves, stems, patches..etc make it a much more complete kit. However, I still feel it is lacking as a complete kit. Both are missing a Valve Stem Puller. To really finish it off, you need the ability to stitch a sidewall. Some tarred twine and sail needle works great for this and can also be used to help lock synthetic rope splices. You could use the insertion needle to push the twine through holes on both sides of the side wall tear as well. A hand drill could be used to make the holes on both sides of the tear, or the reamer could be used to poke the holes. Next you need a way to get the tire off the bead. Breaking the bead can be done with a Hi-Lift, but Tyre Levers are need to get the bead off.
Now the very last recourse would be to use a tube. You would probably have to ruin your rim as the valve stems locations would not line up. To make this work, you'd have to pull a bead, insert the tube in the tire to see where the valve would need to be. Remove tube. Drill new hole. Insert tube. Get the bead back on the rim and inflate. I cannot imagine ever doing this, but it would be better than being stranded.
So the ultimate kit would be:
Tyre Plyers and Levers
Extreme Outback Kit supplemented with the Reamer and Needle from Safety Seal
Tarred Twine or even wire
Tubes
Valve Stem Puller