speaking from distant memory, having owned a Phortess, but not the Ultimate...
They are the same overall design (double sleeved A-pole), the same size, and similar quality.
I think the differences are that the Phortress has plastic rather than bent wire A-connectors, it has a full snow valance all round which the Ultimate doesn't. The Phortress has central ventilation sleeve/tubes at each end, and there are two zips at each end allowing left/centre/right panel opening, The Ultimate has a single central zip at each end. The A-poles on the Phortress may possibly be canted outwards more than on the Ultimate.
Petzl banned lithium AAs in some of their head torches because they have a low internal resistance, and can, if shorted, give a high enough current to set a plastic bodied head torch on fire. This is not good if you've a hood over the top preventing you getting the torch off your head quickly. Later (current) models have a fuse that blows before the fire stage.
The root cause would usually be flexing of the cable to a rear battery pack.
Inner first tents are meant to be stronger because the near continuous deep pole sleeve on something like a Quasar effectively braces one bit of pole against other bits further round the curve, as though you had a lot of short Vango-style tension bands.
An inner first tent like the Ordos, with the inner just clipped to the poles, will be no stronger than an equivalent outer-first tent.
I'd be interested to see how Hille's more recent "sand" colour does. It certainly seems to blend in nicely but I'd want to see one from the inside.
I got a sand Allak just before Christmas, largely because recent green Hillebergs have been such a dark green that they are verging on black. It's actually a mid brown/bronze rather than the pale sand colour that some of the early photos showed, or the somewhat darker shade of sand on the Hilleberg website.
Holding up the empty pole bag against a white cupboard door as a proxy for being inside the tent, the closest readily available match was a bottle of Caol Ila (looking through the whisky).