Dan Durston bei Facebook.
"The X-Dome is comparable in strength to the Portal. I have a Portal here in our workshop (along with quite a few other tents) to benchmark so I have directly compared them. The Portal is a super nice tent and was much stronger than our early prototypes, but we made a lot of improvement over the past couple of years so now the X-Dome is similar or a bit sturdier our tests of strength.
For the pole structure, the X-Dome uses a single spine rather than full dual arch, but the spine portion upsizes the tubing to be about twice as strong, so both pole sets are very similar in strength. The key advantage of the X-Dome is that the poleset connects to the fly whereas the Portal poleset connects to the interior (which is mesh and quite stretchy). So the Portal sorta needs those internal guylines to better anchor/stabilize the poleset because the mesh itself doesn't do a great job of that - and even then the internal guylines don't do that much because it's just one line of tension rather than a full panel of fabric. Whereas the X-Dome the poles are connected to the fly fabric which is much less stretchy/more stable than mesh to better stabilize the poles. For the same size tent the X-Dome is stronger, but the X-Dome is a larger tent (e.g. X-Dome 1+ is way larger than the Portal 1 and similar in overall size to the Portal 2) so the overall result in tests of structural strength/rigidity is very similar results (e.g. the X-Dome 2 is similar in strength to the Portal 2 while being a larger tent). Both tents can support 18-20 lbs on the roof and continue to be within 10% of each other on other ends (e.g. end wall loading).
Where the X-Dome gets ahead is when the trekking poles are added. Both tents can add trekking poles, but in the Portal they can't anchor to the fly edge so they are positioned vertically. That helps with roof loading, but doesn't help much for lateral forces. Whereas in the X-Dome the trekking poles can be angled (counter opposed) and connected to the bottom of the fly walls to directly support the sidewalls and add lateral stability. Also the guylines in the X-Dome directly connect to the poleset, rather than connecting to the fly that is loosely tethered to the poleset. So when you put both tents in 'max' performance mode (guylines, trekking poles etc) the X-Dome is similar or ahead in our tests. If you use the optional heavy duty pole set in the Portal, then it is easily ahead (but that pole set is quite heavy).
For the fabric, I have not strength tested the Portal's fabric (I didn't want to ruin the tent) but this ends up being a bit of a moot point in dome style tents because the stress is so evenly distributed (compared to a trekking pole tent) that you really shouldn't be tearing any of these fabrics. In a storm, the pole set should fail long before the fabrics.
Anyways, all of this is a bit hair splitting because they are both excellent tents and class leading in this area. For example, the MSR Hubba Hubba can support about 6 lbs on the roof while both the Portal and X-Dome are 3x better at about 20 lbs.*
