I feel qualified to give my opinion on your question--having started my own Volvo journey with a 1965 544 Sport (in 1975) and moved on to many 122 models- wagon, 2-door and 4-door (both pre-front disc brake and post).
I loved the 544 - and the 122's. They are similar mechanically - engines, trannies, suspension (although the 122 ball joint front suspension is easier to repair -- and service with way fewer grease fittings) and heating/ventilation systems.
Both models drive and handle alike and offer the same kind of gas mileage (with a nod to the light weight of the 544) and long distance cruising comfort - don't be concerned with the high rpm at modern Interstate speeds - the motor can take it all day - better than most folks ability to deal with the rode noise.
It really comes down to personal preference. Do you prefer the 1930's-1940's look over the raised hood area and low fenders of the 544 - or the 1950's look over the gentle curves of the 122 front (one of my favorite driving memories is the reflections of the trees lining my nearby main street on the black, highly polished hood of our 1964 122 Wagon).
Practically speaking any 122 has better visibility outward and easier access to the trunk for sedans. The seats are different (and different among 122 years) but my problem back (the reason for my move to Volvo in the first place) was comfortable with both models-all years. If practical you should drive both models. Happy Hunting -- Dave