I strongly advise you to drive an Omega. On paper, they are pretty quick, but being quite heavy, they are a bit lazy. Very good from 50mph and pretty untouchable from 100mph..... sadly, we aren't allowed to do that on public roads. You will really miss the torque of the Aero. It goes without saying, the Omega Estate is a 'proper' estate. The 9-5 is a decent size, but the Omega could probably swallow a Saab in it's boot. Seats down, and you've got a van!
Economy...... Don't know how you drive, but my 3.2 wasn't far different to my 2004 9-5 Aero, fuel wise. I have had mine re-mapped though, and like to use the loud pedal. I'm also lugging a LPG system around so on long runs, I'm happy days when it comes to pence per mile.
Ride..... I'd suggest a MV6 over an Elite, else you'll bin it the first roundabout you come to. The Elite is very soft and beautifully comfortable, but corners like the QE2 with a pissed helmsman. The Aero (as you'll know) has lowered and stiffer suspension, just like the MV6.
Seats...... The Saab seats beat the Omega hands down - no question.
Brakes...... Very much dependant on what discs and pads are fitted. Both the Saab and Omega have terrible brakes. The Saab has bigger discs, and is lighter so in theory, should be better.
Servicing & Parts...... Both are comparable. Oil changes every 6k (Aero nearer 3k for me). Suspension is the bugger for the Omega. As is cambelt changes, which is not an issue with the chain driven Saab.
Tech...... The Bose setup sounds great (for it's day) just like the HK setup in the Saab. If either cars have Sat-Nav, they'll be as useless as eachother. Work perfectly well, but no Postcode entry makes them poor compared to modern standards - No recent updates.
Personal Opinion...... I'll always look at an Omega and crave it, but I don't think I'll own another. If my Saab goes pop, I'll definitely buy another.