I would have to say a Softail Heritage. Add a set of Progressive Shocks and you can ride were ever. Just on thing, after a year your wife will had enough of the Sportster and want her own Deluxe. Been there and done it. Now I have her bike (2011 Deluxe), my bike (2000 Heritage), and our bike (2017 Road King). In the garage. Oh, I still have the Sportster, the kids ride it when they want to go ride with us.
Test ride each model and get what you like. I traded a softail heritage for a dyna streetbob. I rode that streetbob on a 4000 mile trip and it was the best bike I had ever ridden . What is comfortable for you is very subjective. You will hear arguments for every bike. Some guys can tour on a sportster comfortably. I never could . Too bad too because man there are some bad *** sportsters out there. Kevin from DK took his 48 on a long tour after he made it more comfortable. Im too beat up now to ride anything but my trike. I miss the dyna every day but am happy to be alive after the big C and riding in spite of some challenges. Be happy , find your ideal bike and ride the thing every chance you get . We are not guaranteed tomorrow. Live each day like it was your last. If I had the budget I would own the trike and a 48 hot rodded out ...just because. But I am a one bike guy.
If you plan on taking longer rides (like all day) where she is riding on the back I would test drive the road glide, and street glide as you can get tour packs to take on and off for a backrest and extra storage. If by long rides you mean a few hours then try out the softail deluxe, softail slim s, road king, fat bob, or a low rider s. So basically, try as many as you can before picking one.