In theory, the Solus 'looks' better on paper - integral rail, recoil lug, "fat" bolt with 60 degree throw, trigger hanger, cut for AW mags.
None of which I've ever really found myself 'needing'. The rail and lug on the Origin are pinned, the 90 degree bolt is maybe a little lighter, and I've never subscribed to the notion of hot-swapping triggers on a field gun, personally. The AW mags are a nice option to have, though.
The Origin is controlled-round feed, with a fixed mechanical ejector, vs the dual plunger design of the Aero. Both have their pros and cons; all I'll say is that dual ejector on a bolt gun just seems... weird. Works, though, by all accounts.
That's about as even-handed as I can be regarding the two. The big difference is the customer support. Aero burned a lot of bridges over the past 12 months, you really can't piss in the well more than Aero did. The local Aero apologist (I'll let you figure out that one on your own) will tell you all about who/what/why, and why you should buy it anyway. On the other hand, if you need support from Zermatt, you can typically get ahold of a *person* in pretty short order. The owner (Ray) frequents the forum here, and is responsive as well. Aero? Good fucking luck.